Leprosy pathophysiology: Difference between revisions

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==Overview==
==Overview==
The clinical manifestations of leprosy largely reflect the [[immune response]] of the host towards the [[infection]]. Once the [[bacterial]] [[cells]] penetrate and multiply within the hosts [[skin]] and [[peripheral nerve]] cells, the [[immune system]] mounts a response toward the [[infected]] [[cells]], which results in clinical [[symptoms]].  Several [[single-nucleotide polymorphism]]s such as [[TNF-α]], [[IL-10]], [[IFN-γ]], [[TLR 1]]  have been associated with a greater susceptibility to leprosy as have other genetic markers.
==Genetics==
The [[infection]] by the [[mycobacterium leprae]] and the course of the [[disease]] are influenced by [[genetic]] factors in the host.<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid18247059">{{cite journal| author=Alter A, Alcaïs A, Abel L, Schurr E| title=Leprosy as a genetic model for susceptibility to common infectious diseases. | journal=Hum Genet | year= 2008 | volume= 123 | issue= 3 | pages= 227-35 | pmid=18247059 | doi=10.1007/s00439-008-0474-z | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18247059  }} </ref> Some [[single-nucleotide polymorphism]] have been associated with a higher [[incidence]] of leprosy. These include:<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid17353895">{{cite journal| author=Alcaïs A, Alter A, Antoni G, Orlova M, Nguyen VT, Singh M et al.| title=Stepwise replication identifies a low-producing lymphotoxin-alpha allele as a major risk factor for early-onset leprosy. | journal=Nat Genet | year= 2007 | volume= 39 | issue= 4 | pages= 517-22 | pmid=17353895 | doi=10.1038/ng2000 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17353895  }} </ref><ref name="pmid12595904">{{cite journal| author=Mira MT, Alcais A, di Pietrantonio T, Thuc NV, Phuong MC, Abel L et al.| title=Segregation of HLA/TNF region is linked to leprosy clinical spectrum in families displaying mixed leprosy subtypes. | journal=Genes Immun | year= 2003 | volume= 4 | issue= 1 | pages= 67-73 | pmid=12595904 | doi=10.1038/sj.gene.6363911 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12595904  }} </ref><ref name="Correa-OliveiraMisch2008">{{cite journal|last1=Correa-Oliveira|first1=Rodrigo|last2=Misch|first2=Elizabeth A.|last3=Macdonald|first3=Murdo|last4=Ranjit|first4=Chaman|last5=Sapkota|first5=Bishwa R.|last6=Wells|first6=Richard D.|last7=Siddiqui|first7=M. Ruby|last8=Kaplan|first8=Gilla|last9=Hawn|first9=Thomas R.|title=Human TLR1 Deficiency Is Associated with Impaired Mycobacterial Signaling and Protection from Leprosy Reversal Reaction|journal=PLoS Neglected Tropical Diseases|volume=2|issue=5|year=2008|pages=e231|issn=1935-2735|doi=10.1371/journal.pntd.0000231}}</ref><ref name="pmid20714752">{{cite journal| author=Cardoso CC, Pereira AC, Brito-de-Souza VN, Dias-Baptista IM, Maniero VC, Venturini J et al.| title=IFNG +874 T>A single nucleotide polymorphism is associated with leprosy among Brazilians. | journal=Hum Genet | year= 2010 | volume= 128 | issue= 5 | pages= 481-90 | pmid=20714752 | doi=10.1007/s00439-010-0872-x | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20714752  }} </ref>
* Low occurrence of a ''lymphotoxin-α-producing'' [[allele]]
* [[Vitamin D]] receptor gene.
* [[TNF-α]] gene
* [[IL-10]] gene
* IFN-γ gene
* [[TLR 1]] gene
Another study has suggested a possible relationship between [[genetic]] variants of the [[NOD2]] [[gene]], increased susceptibility to leprosy and the development of type I and II reactions.<ref name="pmid20350193">{{cite journal| author=Berrington WR, Macdonald M, Khadge S, Sapkota BR, Janer M, Hagge DA et al.| title=Common polymorphisms in the NOD2 gene region are associated with leprosy and its reactive states. | journal=J Infect Dis | year= 2010 | volume= 201 | issue= 9 | pages= 1422-35 | pmid=20350193 | doi=10.1086/651559 | pmc=PMC2853728 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20350193  }} </ref>
It has also been suggested an association between leprosy and a [[locus]] in [[chromosome]] 10p13, in the proximity of the [[mannose receptor]] 1 [[gene]]. Since the [[mannose receptor]]s are located on the [[macrophage]]'s surface, they play an important role in [[phagocytosis]].<ref name="pmid20936290">{{cite journal| author=Alter A, Grant A, Abel L, Alcaïs A, Schurr E| title=Leprosy as a genetic disease. | journal=Mamm Genome | year= 2011 | volume= 22 | issue= 1-2 | pages= 19-31 | pmid=20936290 | doi=10.1007/s00335-010-9287-1 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20936290  }} </ref>
Additionally, the subtype of leprosy developed in a patient has been associated with [[genes]] of the class II [[HLA]]/[[major histocompatibility complex]], at [[chromosome 6]]. Accordingly:
* [[HLA-DR2]] and [[HLA-DR3]] are considered to be linked with the tuberculoid class.
* [[HLA-DQ1]] is considered to be linked with the lepromatous class.


==Pathogenesis==
==Pathogenesis==
[[Mycobacterium leprae]] has predisposition to [[infect]] [[macrophages]]. It is usually collected inside these, in [[intracellular]] groups, also called ''globi''. This [[organism]] has an ideal growth temperature of 27-30ºC, which explains why it usually [[infection|infects]] areas such as the [[skin]], [[upper respiratory]] [[mucosa]] and [[peripheral nerves]]. It is able to [[infect]] [[cells]], particularly due to 2 structures:<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref><ref name="pmid23870850">{{cite journal| author=Eichelmann K, González González SE, Salas-Alanis JC, Ocampo-Candiani J| title=Leprosy. An update: definition, pathogenesis, classification, diagnosis, and treatment. | journal=Actas Dermosifiliogr | year= 2013 | volume= 104 | issue= 7 | pages= 554-63 | pmid=23870850 | doi=10.1016/j.adengl.2012.03.028 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23870850  }} </ref><ref name="BrittonLockwood2004">{{cite journal|last1=Britton|first1=Warwick J|last2=Lockwood|first2=Diana NJ|title=Leprosy|journal=The Lancet|volume=363|issue=9416|year=2004|pages=1209–1219|issn=01406736|doi=10.1016/S0140-6736(04)15952-7}}</ref><ref name="GuliaFried2010">{{cite journal|last1=Gulia|first1=Andrea|last2=Fried|first2=Isabella|last3=Massone|first3=Cesare|title=New insights in the pathogenesis and genetics of leprosy|journal=F1000 Medicine Reports|volume=2|year=2010|issn=17575931|doi=10.3410/M2-30}}</ref>
[[Mycobacterium leprae]] has predisposition to [[infect]] [[macrophages]]. It is usually collected inside these, in [[intracellular]] groups, called ''globi''. This [[organism]] has an ideal growth temperature of 27-30ºC, which explains why it usually [[infection|infects]] areas such as the [[skin]], [[upper respiratory]] [[mucosa]] and [[peripheral nerves]]. It is able to [[infect]] [[cells]], particularly due to 2 structures:<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref><ref name="pmid23870850">{{cite journal| author=Eichelmann K, González González SE, Salas-Alanis JC, Ocampo-Candiani J| title=Leprosy. An update: definition, pathogenesis, classification, diagnosis, and treatment. | journal=Actas Dermosifiliogr | year= 2013 | volume= 104 | issue= 7 | pages= 554-63 | pmid=23870850 | doi=10.1016/j.adengl.2012.03.028 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23870850  }} </ref><ref name="BrittonLockwood2004">{{cite journal|last1=Britton|first1=Warwick J|last2=Lockwood|first2=Diana NJ|title=Leprosy|journal=The Lancet|volume=363|issue=9416|year=2004|pages=1209–1219|issn=01406736|doi=10.1016/S0140-6736(04)15952-7}}</ref><ref name="GuliaFried2010">{{cite journal|last1=Gulia|first1=Andrea|last2=Fried|first2=Isabella|last3=Massone|first3=Cesare|title=New insights in the pathogenesis and genetics of leprosy|journal=F1000 Medicine Reports|volume=2|year=2010|issn=17575931|doi=10.3410/M2-30}}</ref>


* [[Capsule]] - target of intense humoral immune response (immunoglobulin M-mediated).  
* [[Capsule]] - target of intense humoral immune response (immunoglobulin M-mediated).  
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The [[bacillus]] is known to target [[Schwann cells]], specifically the G domain of the [[laminin]]-α2 chain. This domain is predominantly expressed in the [[basal lamina]] of [[peripheral nerves]], thereby explaining the [[neuropathy]] felt in this condition. The [[pathogen]] then penetrates the [[cell]], at which time it will multiply, until the [[infected]] [[cell]] is finally recognized by the [[immune system]] and a an [[inflammatory]] reaction is started.<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref><ref name="pmid10449784">{{cite journal| author=Shimoji Y, Ng V, Matsumura K, Fischetti VA, Rambukkana A| title=A 21-kDa surface protein of Mycobacterium leprae binds peripheral nerve laminin-2 and mediates Schwann cell invasion. | journal=Proc Natl Acad Sci U S A | year= 1999 | volume= 96 | issue= 17 | pages= 9857-62 | pmid=10449784 | doi= | pmc=PMC22300 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10449784  }} </ref>
The [[bacillus]] is known to target [[Schwann cells]], specifically the G domain of the [[laminin]]-α2 chain. This domain is predominantly expressed in the [[basal lamina]] of [[peripheral nerves]], thereby explaining the [[neuropathy]] felt in this condition. The [[pathogen]] then penetrates the [[cell]], at which time it will multiply, until the [[infected]] [[cell]] is finally recognized by the [[immune system]] and a an [[inflammatory]] reaction is started.<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref><ref name="pmid10449784">{{cite journal| author=Shimoji Y, Ng V, Matsumura K, Fischetti VA, Rambukkana A| title=A 21-kDa surface protein of Mycobacterium leprae binds peripheral nerve laminin-2 and mediates Schwann cell invasion. | journal=Proc Natl Acad Sci U S A | year= 1999 | volume= 96 | issue= 17 | pages= 9857-62 | pmid=10449784 | doi= | pmc=PMC22300 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10449784  }} </ref>


This mechanism explains the reason why the clinical manifestations of the disease will depend on the [[immunologic]] status of the patient and the intensity of the response developed following the [[infection]] of the host [[cells]].<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref>
This mechanism explains the reason why the clinical manifestations of the disease will depend on the immunologic status of the patient and the intensity of the response developed following the [[infection]] of the host [[cells]].<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref>


==Genetics==
==Transmission==
The [[infection]] by the [[mycobacterium leprae]] and the course of the [[disease]] are influenced by certain [[genetic]] factors of the host.<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid18247059">{{cite journal| author=Alter A, Alcaïs A, Abel L, Schurr E| title=Leprosy as a genetic model for susceptibility to common infectious diseases. | journal=Hum Genet | year= 2008 | volume= 123 | issue= 3 | pages= 227-35 | pmid=18247059 | doi=10.1007/s00439-008-0474-z | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18247059 }} </ref> Some [[single-nucleotide polymorphism]] have been associated with a higher [[incidence]] of leprosy. These include:<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid17353895">{{cite journal| author=Alcaïs A, Alter A, Antoni G, Orlova M, Nguyen VT, Singh M et al.| title=Stepwise replication identifies a low-producing lymphotoxin-alpha allele as a major risk factor for early-onset leprosy. | journal=Nat Genet | year= 2007 | volume= 39 | issue= 4 | pages= 517-22 | pmid=17353895 | doi=10.1038/ng2000 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17353895 }} </ref><ref name="pmid12595904">{{cite journal| author=Mira MT, Alcais A, di Pietrantonio T, Thuc NV, Phuong MC, Abel L et al.| title=Segregation of HLA/TNF region is linked to leprosy clinical spectrum in families displaying mixed leprosy subtypes. | journal=Genes Immun | year= 2003 | volume= 4 | issue= 1 | pages= 67-73 | pmid=12595904 | doi=10.1038/sj.gene.6363911 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12595904 }} </ref><ref name="Correa-OliveiraMisch2008">{{cite journal|last1=Correa-Oliveira|first1=Rodrigo|last2=Misch|first2=Elizabeth A.|last3=Macdonald|first3=Murdo|last4=Ranjit|first4=Chaman|last5=Sapkota|first5=Bishwa R.|last6=Wells|first6=Richard D.|last7=Siddiqui|first7=M. Ruby|last8=Kaplan|first8=Gilla|last9=Hawn|first9=Thomas R.|title=Human TLR1 Deficiency Is Associated with Impaired Mycobacterial Signaling and Protection from Leprosy Reversal Reaction|journal=PLoS Neglected Tropical Diseases|volume=2|issue=5|year=2008|pages=e231|issn=1935-2735|doi=10.1371/journal.pntd.0000231}}</ref><ref name="pmid20714752">{{cite journal| author=Cardoso CC, Pereira AC, Brito-de-Souza VN, Dias-Baptista IM, Maniero VC, Venturini J et al.| title=IFNG +874 T>A single nucleotide polymorphism is associated with leprosy among Brazilians. | journal=Hum Genet | year= 2010 | volume= 128 | issue= 5 | pages= 481-90 | pmid=20714752 | doi=10.1007/s00439-010-0872-x | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20714752  }} </ref>
The locations of the body thought to be the source of [[transmission]] of ''[[Mycobacterium leprae]]'' include:
* Low occurrence of a ''lymphotoxin-α-producing'' [[allele]].
* '''''Skin''''' - studies have shown presence of large amounts of [[bacteria]] in the [[dermis]] of leprosy patients, however, it is not known if these are able to reach the [[epidermis]] in order to be [[transmission|transmitted]] to other individuals.<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid16779736">{{cite journal| author=Scollard DM, Joyce MP, Gillis TP| title=Development of leprosy and type 1 leprosy reactions after treatment with infliximab: a report of 2 cases. | journal=Clin Infect Dis | year= 2006 | volume= 43 | issue= 2 | pages= e19-22 | pmid=16779736 | doi=10.1086/505222 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16779736 }} </ref> Conflicting reports have been issued on this matter, therefore whether or not the bacteria are able to reach the cell surface, remains uncertain.<ref name="pmid16248207">{{cite journal| author=Truman R| title=Leprosy in wild armadillos. | journal=Lepr Rev | year= 2005 | volume= 76 | issue= 3 | pages= 198-208 | pmid=16248207 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16248207  }} </ref>A study showed presence of these organisms in sebaceous secretions of lepromatous leprosy patients, which leads to the hypothesis that these pathogens may exist the host's body through this manner.<ref name="pmid9728446">{{cite journal| author=Valverde CR, Canfield D, Tarara R, Esteves MI, Gormus BJ| title=Spontaneous leprosy in a wild-caught cynomolgus macaque. | journal=Int J Lepr Other Mycobact Dis | year= 1998 | volume= 66 | issue= 2 | pages= 140-8 | pmid=9728446 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9728446 }} </ref>
* Vitamin D receptor gene.
* '''''Nasal mucosa''''' - [[secretions]] from the [[nasal mucosa]] of ''lepromatous patients'' are rich in viable [[mycobacterium leprae]], and may therefore be a source of [[transmission]].<ref name="pmid19994470">{{cite journal| author=Gillis T, Vissa V, Matsuoka M, Young S, Richardus JH, Truman R et al.| title=Characterisation of short tandem repeats for genotyping Mycobacterium leprae. | journal=Lepr Rev | year= 2009 | volume= 80 | issue= 3 | pages= 250-60 | pmid=19994470 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19994470 }} </ref><ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref>
* TNF-α [[gene]].
The entry route into the [[human body]] is also still unknown, however, recent studies point to a predominance of the [[respiratory]] route as well.<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid22270197">{{cite journal| author=Han XY, Sizer KC, Tan HH| title=Identification of the leprosy agent Mycobacterium lepromatosis in Singapore. | journal=J Drugs Dermatol | year= 2012 | volume= 11 | issue= 2 | pages= 168-72 | pmid=22270197 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22270197 }} </ref><ref name="pmid19633074">{{cite journal| author=Han XY, Sizer KC, Thompson EJ, Kabanja J, Li J, Hu P et al.| title=Comparative sequence analysis of Mycobacterium leprae and the new leprosy-causing Mycobacterium lepromatosis. | journal=J Bacteriol | year= 2009 | volume= 191 | issue= 19 | pages= 6067-74 | pmid=19633074 | doi=10.1128/JB.00762-09 | pmc=PMC2747882 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19633074 }} </ref>
* IL-10 [[gene]].
* IFN-γ [[gene]].
* TLR 1 [[gene]].
Another study has also suggested a possible relationship between [[genetic]] variants of the NOD2 [[gene]] and increased susceptibility to leprosy and the development of type I and II reactions.<ref name="pmid20350193">{{cite journal| author=Berrington WR, Macdonald M, Khadge S, Sapkota BR, Janer M, Hagge DA et al.| title=Common polymorphisms in the NOD2 gene region are associated with leprosy and its reactive states. | journal=J Infect Dis | year= 2010 | volume= 201 | issue= 9 | pages= 1422-35 | pmid=20350193 | doi=10.1086/651559 | pmc=PMC2853728 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20350193 }} </ref>
 
It has also been suggested an association between leprosy and a [[locus]] in [[chromosome]] 10p13, in the proximity of the [[mannose receptor]] 1 [[gene]]  since the [[mannose receptor]]s located on [[macrophage]]'s surface play an important role in [[phagocytosis]].<ref name="pmid20936290">{{cite journal| author=Alter A, Grant A, Abel L, Alcaïs A, Schurr E| title=Leprosy as a genetic disease. | journal=Mamm Genome | year= 2011 | volume= 22 | issue= 1-2 | pages= 19-31 | pmid=20936290 | doi=10.1007/s00335-010-9287-1 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20936290 }} </ref>
 
Additionally, the class of leprosy developed in a patient has been associated with [[genes]] of the class II [[HLA]]/[[major histocompatibility complex]], at [[chromosome 6]]. Accordingly:
* [[HLA-DR2]] and [[HLA-DR3]] are considered to be linked with the tuberculoid class.
* [[HLA-DQ1]] is considered to be linked with the lepromatous class.


==Associated Conditions==
==Associated Conditions==
===Association with HIV===
===Leprosy Among Patients with HIV===
Although previously suspected, there is no increased susceptibility to Mycobacterium leprae in HIV patients, nor are the clinical manifestations altered. The only apparent relationship between these two conditions is the manifestation of latent leprosy, in HIV patients, once the immense response is reestablished after initiation of antiretroviral therapy.<ref name="WalkerLockwood2007">{{cite journal|last1=Walker|first1=Stephen L.|last2=Lockwood|first2=Dina N.J.|title=Leprosy|journal=Clinics in Dermatology|volume=25|issue=2|year=2007|pages=165–172|issn=0738081X|doi=10.1016/j.clindermatol.2006.05.012}}</ref>
There is no increased susceptibility to [[Mycobacterium leprae]] in [[HIV]] patients, nor are the clinical features altered. After initiation of [[antiretroviral therapy]], latent leprosy can become clinically apparent in an [[HIV]] patient once the [[immune response]] is reestablished.<ref name="WalkerLockwood2007">{{cite journal|last1=Walker|first1=Stephen L.|last2=Lockwood|first2=Dina N.J.|title=Leprosy|journal=Clinics in Dermatology|volume=25|issue=2|year=2007|pages=165–172|issn=0738081X|doi=10.1016/j.clindermatol.2006.05.012}}</ref><ref name="pmid16728321">{{cite journal| author=Ustianowski AP, Lawn SD, Lockwood DN| title=Interactions between HIV infection and leprosy: a paradox. | journal=Lancet Infect Dis | year= 2006 | volume= 6 | issue= 6 | pages= 350-60 | pmid=16728321 | doi=10.1016/S1473-3099(06)70493-5 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16728321  }} </ref>


==Gross Pathology==
==Gross Pathology==
Line 41: Line 48:


====Tuberculoid Leprosy====
====Tuberculoid Leprosy====
* May resolve spontaneously.
* May resolve spontaneously
* Well-defined [[macules]].
* Well-defined [[macules]]
* [[hypopigmentation|Hypopigmented]] [[skin lesions]].
* [[hypopigmentation|Hypopigmented]] [[skin lesions]]
* Borders of lesions are commonly [[erythematous]] and elevated, with depressed centers.
* Borders of lesions are commonly [[erythematous]] and elevated, with depressed centers
* [[Sensation]] on the [[face]] commonly unaffected.
* [[Sensation]] on the [[face]] commonly unaffected
* Anhydrosis.
* [[Anhidrosis]]
* Loss of adnexal structures.
* Loss of adnexal structures


====Lepromatous Leprosy====
====Lepromatous Leprosy====
* [[Papules]] and [[nodules]], usually bilateral, symmetrical with ovoid shape.
* [[Papules]] and [[nodules]], usually bilateral, symmetrical with ovoid shape
* [[Leonine facies]].
* [[Leonine facies]]
* Severe nerve involvement.
* Severe nerve involvement


===Immunologic Reactions===
===Immunologic Reactions===
Systemic [[inflammatory]] reactions may occur before, during or after the [[therapy|treatment]] of leprosy.<ref name="pmid6219136">{{cite journal| author=Modlin RL, Hofman FM, Taylor CR, Rea TH| title=T lymphocyte subsets in the skin lesions of patients with leprosy. | journal=J Am Acad Dermatol | year= 1983 | volume= 8 | issue= 2 | pages= 182-9 | pmid=6219136 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6219136  }} </ref> These are thought to be related to changes in the immune system, such as following stress situations, pregnancy or leprosy medications.<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref> There are two different types of reactions, which are thought to have different underlying immunologic mechanisms.
Systemic [[inflammatory]] reactions may occur before, during or after the [[therapy|treatment]] of leprosy.<ref name="pmid6219136">{{cite journal| author=Modlin RL, Hofman FM, Taylor CR, Rea TH| title=T lymphocyte subsets in the skin lesions of patients with leprosy. | journal=J Am Acad Dermatol | year= 1983 | volume= 8 | issue= 2 | pages= 182-9 | pmid=6219136 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6219136  }} </ref> These are thought to be related to changes in the [[immune system]], such as following stressful situations, [[pregnancy]] or leprosy medications.<ref name="EichelmannGonzález González2013">{{cite journal|last1=Eichelmann|first1=K.|last2=González González|first2=S.E.|last3=Salas-Alanis|first3=J.C.|last4=Ocampo-Candiani|first4=J.|title=Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment|journal=Actas Dermo-Sifiliográficas (English Edition)|volume=104|issue=7|year=2013|pages=554–563|issn=15782190|doi=10.1016/j.adengl.2012.03.028}}</ref> There are two different types of reactions, which are thought to have different underlying immunologic mechanisms:


====Tipe 1 (T1R) or Reversal Reaction (RR)====
====Tipe 1 (T1R) or Reversal Reaction (RR)====
* Predominant in borderline [[disease]].
* Predominant in borderline [[disease]]
* Predominant [[type IV hypersensitivity]].<ref name="BalagonGelber2010">{{cite journal|last1=Balagon|first1=M. V. F.|last2=Gelber|first2=R. H.|last3=Abalos|first3=R. M.|last4=Cellona|first4=R. V.|title=Reactions Following Completion of 1 and 2 Year Multidrug Therapy (MDT)|journal=American Journal of Tropical Medicine and Hygiene|volume=83|issue=3|year=2010|pages=637–644|issn=0002-9637|doi=10.4269/ajtmh.2010.09-0586}}</ref>
* Predominant [[type IV hypersensitivity]]<ref name="BalagonGelber2010">{{cite journal|last1=Balagon|first1=M. V. F.|last2=Gelber|first2=R. H.|last3=Abalos|first3=R. M.|last4=Cellona|first4=R. V.|title=Reactions Following Completion of 1 and 2 Year Multidrug Therapy (MDT)|journal=American Journal of Tropical Medicine and Hygiene|volume=83|issue=3|year=2010|pages=637–644|issn=0002-9637|doi=10.4269/ajtmh.2010.09-0586}}</ref>
* Red patches developing in previous [[skin lesions]], commonly on the [[face]] or [[nerve]] trunks.
* Red patches developing in previous [[skin lesions]], commonly on the [[face]] or [[nerve]] trunks
* [[Erythema]] of previous [[skin lesions]].
* [[Erythema]] of previous [[skin lesions]]
* [[Inflammation]] may lead to [[nerve]] lesion and [[paralysis]].
* [[Inflammation]] may lead to [[nerve]] lesion and [[paralysis]]
* [[Edema]] of [[hands]] and [[feet]].
* [[Edema]] of [[hands]] and [[feet]]
* [[Arthralgia]], predominantly of smaller [[joints]].
* [[Arthralgia]], predominantly of smaller [[joints]]
* [[Ulcer|Ulcerated]] lesions.
* [[Ulcer|Ulcerated]] lesions
* [[Pain]] or [[tenderness]] on [[lesions]].
* [[Pain]] or [[tenderness]] on [[lesions]]


====Type 2 (T2R) or Erythema Nodosum Leprosum (ENL)====
====Type 2 (T2R) or Erythema Nodosum Leprosum (ENL)====
* Predominant in lepromatous disease.
* Predominant in lepromatous disease
* Predominant [[type III hypersensitivity]].
* Predominant [[type III hypersensitivity]]
* Sudden occurrence of painful [[nodules]].
* Sudden occurrence of painful [[nodules]]
* Nodules may lead to [[pustules]] or ulcers.
* [[Nodules]] may lead to [[pustules]] or ulcers
* [[Pustules]] may discharge pus containing [[polymorphonuclear cells]] and degenerating [[mycobacteria]].
* [[Pustules]] may discharge [[pus]] containing [[polymorphonuclear cells]] and degenerating [[mycobacteria]]
* After [[lesions]] resolve, brawn [[skin lesions]] may remain.
* After [[lesions]] resolve, brawn [[skin lesions]] may remain
* Occasionally may occur: [[orchitis]], [[muscle]] and [[lymphadenopathy]] [[tenderness]] and/or swollen [[joints]].
* Occasionally may occur: [[orchitis]], [[muscle]] and [[lymphadenopathy]] [[tenderness]] and/or swollen [[joints]]
* Without treatment usually lasts for 2 weeks.
* Without treatment usually lasts for 2 weeks


==Microscopic Pathology==
==Microscopic Pathology==
===Histopathology===
===Histopathology===
The manifestations of leprosy depend on the host's [[immune response]] towards the [[mycobacteria]]. Therefore, ''tuberculoid'' and ''lepromatous'' patients will show different histopathologic findings:<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid6219136">{{cite journal| author=Modlin RL, Hofman FM, Taylor CR, Rea TH| title=T lymphocyte subsets in the skin lesions of patients with leprosy. | journal=J Am Acad Dermatol | year= 1983 | volume= 8 | issue= 2 | pages= 182-9 | pmid=6219136 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6219136  }} </ref><ref name="pmid6332791">{{cite journal| author=Wallach D, Flageul B, Bach MA, Cottenot F| title=The cellular content of dermal leprous granulomas: an immuno-histological approach. | journal=Int J Lepr Other Mycobact Dis | year= 1984 | volume= 52 | issue= 3 | pages= 318-26 | pmid=6332791 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6332791  }} </ref>
The clinical manifestations of leprosy depend on the host's [[immune response]] towards the [[mycobacteria]]. Therefore, ''tuberculoid'' and ''lepromatous'' patients will show different [[histopathologic]] findings:<ref name="BhatPrakash2012">{{cite journal|last1=Bhat|first1=Ramesh Marne|last2=Prakash|first2=Chaitra|title=Leprosy: An Overview of Pathophysiology|journal=Interdisciplinary Perspectives on Infectious Diseases|volume=2012|year=2012|pages=1–6|issn=1687-708X|doi=10.1155/2012/181089}}</ref><ref name="pmid6219136">{{cite journal| author=Modlin RL, Hofman FM, Taylor CR, Rea TH| title=T lymphocyte subsets in the skin lesions of patients with leprosy. | journal=J Am Acad Dermatol | year= 1983 | volume= 8 | issue= 2 | pages= 182-9 | pmid=6219136 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6219136  }} </ref><ref name="pmid6332791">{{cite journal| author=Wallach D, Flageul B, Bach MA, Cottenot F| title=The cellular content of dermal leprous granulomas: an immuno-histological approach. | journal=Int J Lepr Other Mycobact Dis | year= 1984 | volume= 52 | issue= 3 | pages= 318-26 | pmid=6332791 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6332791  }} </ref>
* Tuberculoid patients - These patients will show a strong [[immune response]] towards the [[bacteria]], with production of IFN-γ and commonly showing a positive [[lepromin]] [[skin test]].
====Tuberculoid patients====
:* [[Inflammatory]] infiltrate with multiple [[granulomas]].
These patients will show a strong [[immune response]] towards the [[bacteria]], with:
:* [[Granulomas]] containing [[giant cells]], differentiated macrophages and epithelioid cells.
* Production of [[IFN-γ]]
:* Predominance of CD4 cells.
* [[Inflammatory]] infiltrate with multiple [[granulomas]]
:* Low [[bacterial]] index.
* [[Granulomas]] containing [[giant cells]], differentiated [[macrophage]]s and epithelioid cells
* Predominance of [[CD4]] cells
* Low [[bacterial]] index
* Commonly positive [[lepromin]] [[skin test]]
 
====Lepromatous patients====
These patients will show a weaker [[immune response]], with:
* Weak [[Cell-mediated immunity|cell-mediated response]]
* Absence of [[granulomas]]
* Straightened [[skin]]
* Predominance of [[CD8]] [[cells]]
* High [[bacterial]] index
 
==Gallery==
<gallery>
Image:Leprosy-18.jpg|Case of lepromatous or multibacillary leprosy, with photomicrograph revealing histopathologic changes in human testicular tissue, including a large number of “foam cells”. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
Image:Leprosy-27.jpg|Acid-fast-stained photomicrograph of tissue sample from a patient with leprosy, revealing chronic inflammatory lesion (granuloma) within which numerous red-colored Mycobacterium leprae bacteria are visible. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
Image:Leprosy-28.jpg|Photomicrograph of a skin tissue sample from patient with leprosy revealing cutaneous nerve, which had been invaded by numerous Mycobacterium leprae bacteria. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>


* Lepromatous patients - These patients will show a weaker [[immune response]] towards the [[bacteria]], particularly a weak cell-mediated response.
Image:Leprosy-30.jpg|Photomicrograph of histopathologic changes in skin section extracted from a case of leprosy, possibly tuberculoid form, is uncertain. Note depicted here a nerve, which had been surrounded by dense infiltrate of undifferentiated histiocytes and many lymphocytes. The nerve sheath and endoneural region were also infiltrated. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
:* Absence of [[granulomas]].
 
:* Straightened skin.
Image:Leprosy-34.jpg|Light photomicrograph revealing histopathologic cytoarchitectural characteristics in a mycobacterial skin infection. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
:* Predominance of CD8 cells.
 
:* High [[bacterial]] index.
Image:Leprosy-35.jpg|Light photomicrograph revealing histopathologic cytoarchitectural characteristics seen in mycobacterial skin infection. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
Image:Leprosy-36.jpg|Light photomicrograph revealing histopathologic cytoarchitectural characteristics seen in mycobacterial skin infection. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
Image:Leprosy-37.jpg|Light photomicrograph revealing histopathologic cytoarchitectural characteristics seen in mycobacterial skin infection. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
Image:Leprosy-38.jpg|Light photomicrograph revealing histopathologic cytoarchitectural characteristics seen in mycobacterial skin infection. <SMALL><SMALL>''[http://phil.cdc.gov/phil/  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/}}</ref></SMALL></SMALL>
 
</gallery>


==References==
==References==
Line 101: Line 135:
[[Category:Disease]]
[[Category:Disease]]
[[Category:Dermatology]]
[[Category:Dermatology]]
[[Category:Infectious disease]]
 
[[Category:Tropical disease]]
[[Category:Tropical disease]]
[[Category:Leprosy]]
[[Category:Leprosy]]

Latest revision as of 18:10, 18 September 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

The clinical manifestations of leprosy largely reflect the immune response of the host towards the infection. Once the bacterial cells penetrate and multiply within the hosts skin and peripheral nerve cells, the immune system mounts a response toward the infected cells, which results in clinical symptoms. Several single-nucleotide polymorphisms such as TNF-α, IL-10, IFN-γ, TLR 1 have been associated with a greater susceptibility to leprosy as have other genetic markers.

Genetics

The infection by the mycobacterium leprae and the course of the disease are influenced by genetic factors in the host.[1][2] Some single-nucleotide polymorphism have been associated with a higher incidence of leprosy. These include:[1][3][4][5][6]

Another study has suggested a possible relationship between genetic variants of the NOD2 gene, increased susceptibility to leprosy and the development of type I and II reactions.[7]

It has also been suggested an association between leprosy and a locus in chromosome 10p13, in the proximity of the mannose receptor 1 gene. Since the mannose receptors are located on the macrophage's surface, they play an important role in phagocytosis.[8]

Additionally, the subtype of leprosy developed in a patient has been associated with genes of the class II HLA/major histocompatibility complex, at chromosome 6. Accordingly:

  • HLA-DR2 and HLA-DR3 are considered to be linked with the tuberculoid class.
  • HLA-DQ1 is considered to be linked with the lepromatous class.

Pathogenesis

Mycobacterium leprae has predisposition to infect macrophages. It is usually collected inside these, in intracellular groups, called globi. This organism has an ideal growth temperature of 27-30ºC, which explains why it usually infects areas such as the skin, upper respiratory mucosa and peripheral nerves. It is able to infect cells, particularly due to 2 structures:[9][10][11][12]

  • Capsule - target of intense humoral immune response (immunoglobulin M-mediated).

The bacillus is known to target Schwann cells, specifically the G domain of the laminin-α2 chain. This domain is predominantly expressed in the basal lamina of peripheral nerves, thereby explaining the neuropathy felt in this condition. The pathogen then penetrates the cell, at which time it will multiply, until the infected cell is finally recognized by the immune system and a an inflammatory reaction is started.[9][13]

This mechanism explains the reason why the clinical manifestations of the disease will depend on the immunologic status of the patient and the intensity of the response developed following the infection of the host cells.[9]

Transmission

The locations of the body thought to be the source of transmission of Mycobacterium leprae include:

  • Skin - studies have shown presence of large amounts of bacteria in the dermis of leprosy patients, however, it is not known if these are able to reach the epidermis in order to be transmitted to other individuals.[1][14] Conflicting reports have been issued on this matter, therefore whether or not the bacteria are able to reach the cell surface, remains uncertain.[15]A study showed presence of these organisms in sebaceous secretions of lepromatous leprosy patients, which leads to the hypothesis that these pathogens may exist the host's body through this manner.[16]
  • Nasal mucosa - secretions from the nasal mucosa of lepromatous patients are rich in viable mycobacterium leprae, and may therefore be a source of transmission.[17][1]

The entry route into the human body is also still unknown, however, recent studies point to a predominance of the respiratory route as well.[1][18][19]

Associated Conditions

Leprosy Among Patients with HIV

There is no increased susceptibility to Mycobacterium leprae in HIV patients, nor are the clinical features altered. After initiation of antiretroviral therapy, latent leprosy can become clinically apparent in an HIV patient once the immune response is reestablished.[20][21]

Gross Pathology

Type of Leprosy

Tuberculoid Leprosy

Lepromatous Leprosy

Immunologic Reactions

Systemic inflammatory reactions may occur before, during or after the treatment of leprosy.[22] These are thought to be related to changes in the immune system, such as following stressful situations, pregnancy or leprosy medications.[9] There are two different types of reactions, which are thought to have different underlying immunologic mechanisms:

Tipe 1 (T1R) or Reversal Reaction (RR)

Type 2 (T2R) or Erythema Nodosum Leprosum (ENL)

Microscopic Pathology

Histopathology

The clinical manifestations of leprosy depend on the host's immune response towards the mycobacteria. Therefore, tuberculoid and lepromatous patients will show different histopathologic findings:[1][22][24]

Tuberculoid patients

These patients will show a strong immune response towards the bacteria, with:

Lepromatous patients

These patients will show a weaker immune response, with:

Gallery

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Bhat, Ramesh Marne; Prakash, Chaitra (2012). "Leprosy: An Overview of Pathophysiology". Interdisciplinary Perspectives on Infectious Diseases. 2012: 1–6. doi:10.1155/2012/181089. ISSN 1687-708X.
  2. ↑ Alter A, Alcaïs A, Abel L, Schurr E (2008). "Leprosy as a genetic model for susceptibility to common infectious diseases". Hum Genet. 123 (3): 227–35. doi:10.1007/s00439-008-0474-z. PMID 18247059.
  3. ↑ Alcaïs A, Alter A, Antoni G, Orlova M, Nguyen VT, Singh M; et al. (2007). "Stepwise replication identifies a low-producing lymphotoxin-alpha allele as a major risk factor for early-onset leprosy". Nat Genet. 39 (4): 517–22. doi:10.1038/ng2000. PMID 17353895.
  4. ↑ Mira MT, Alcais A, di Pietrantonio T, Thuc NV, Phuong MC, Abel L; et al. (2003). "Segregation of HLA/TNF region is linked to leprosy clinical spectrum in families displaying mixed leprosy subtypes". Genes Immun. 4 (1): 67–73. doi:10.1038/sj.gene.6363911. PMID 12595904.
  5. ↑ Correa-Oliveira, Rodrigo; Misch, Elizabeth A.; Macdonald, Murdo; Ranjit, Chaman; Sapkota, Bishwa R.; Wells, Richard D.; Siddiqui, M. Ruby; Kaplan, Gilla; Hawn, Thomas R. (2008). "Human TLR1 Deficiency Is Associated with Impaired Mycobacterial Signaling and Protection from Leprosy Reversal Reaction". PLoS Neglected Tropical Diseases. 2 (5): e231. doi:10.1371/journal.pntd.0000231. ISSN 1935-2735.
  6. ↑ Cardoso CC, Pereira AC, Brito-de-Souza VN, Dias-Baptista IM, Maniero VC, Venturini J; et al. (2010). "IFNG +874 T>A single nucleotide polymorphism is associated with leprosy among Brazilians". Hum Genet. 128 (5): 481–90. doi:10.1007/s00439-010-0872-x. PMID 20714752.
  7. ↑ Berrington WR, Macdonald M, Khadge S, Sapkota BR, Janer M, Hagge DA; et al. (2010). "Common polymorphisms in the NOD2 gene region are associated with leprosy and its reactive states". J Infect Dis. 201 (9): 1422–35. doi:10.1086/651559. PMC 2853728. PMID 20350193.
  8. ↑ Alter A, Grant A, Abel L, Alcaïs A, Schurr E (2011). "Leprosy as a genetic disease". Mamm Genome. 22 (1–2): 19–31. doi:10.1007/s00335-010-9287-1. PMID 20936290.
  9. ↑ 9.0 9.1 9.2 9.3 Eichelmann, K.; González González, S.E.; Salas-Alanis, J.C.; Ocampo-Candiani, J. (2013). "Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment". Actas Dermo-Sifiliográficas (English Edition). 104 (7): 554–563. doi:10.1016/j.adengl.2012.03.028. ISSN 1578-2190.
  10. ↑ Eichelmann K, González González SE, Salas-Alanis JC, Ocampo-Candiani J (2013). "Leprosy. An update: definition, pathogenesis, classification, diagnosis, and treatment". Actas Dermosifiliogr. 104 (7): 554–63. doi:10.1016/j.adengl.2012.03.028. PMID 23870850.
  11. ↑ Britton, Warwick J; Lockwood, Diana NJ (2004). "Leprosy". The Lancet. 363 (9416): 1209–1219. doi:10.1016/S0140-6736(04)15952-7. ISSN 0140-6736.
  12. ↑ Gulia, Andrea; Fried, Isabella; Massone, Cesare (2010). "New insights in the pathogenesis and genetics of leprosy". F1000 Medicine Reports. 2. doi:10.3410/M2-30. ISSN 1757-5931.
  13. ↑ Shimoji Y, Ng V, Matsumura K, Fischetti VA, Rambukkana A (1999). "A 21-kDa surface protein of Mycobacterium leprae binds peripheral nerve laminin-2 and mediates Schwann cell invasion". Proc Natl Acad Sci U S A. 96 (17): 9857–62. PMC 22300. PMID 10449784.
  14. ↑ Scollard DM, Joyce MP, Gillis TP (2006). "Development of leprosy and type 1 leprosy reactions after treatment with infliximab: a report of 2 cases". Clin Infect Dis. 43 (2): e19–22. doi:10.1086/505222. PMID 16779736.
  15. ↑ Truman R (2005). "Leprosy in wild armadillos". Lepr Rev. 76 (3): 198–208. PMID 16248207.
  16. ↑ Valverde CR, Canfield D, Tarara R, Esteves MI, Gormus BJ (1998). "Spontaneous leprosy in a wild-caught cynomolgus macaque". Int J Lepr Other Mycobact Dis. 66 (2): 140–8. PMID 9728446.
  17. ↑ Gillis T, Vissa V, Matsuoka M, Young S, Richardus JH, Truman R; et al. (2009). "Characterisation of short tandem repeats for genotyping Mycobacterium leprae". Lepr Rev. 80 (3): 250–60. PMID 19994470.
  18. ↑ Han XY, Sizer KC, Tan HH (2012). "Identification of the leprosy agent Mycobacterium lepromatosis in Singapore". J Drugs Dermatol. 11 (2): 168–72. PMID 22270197.
  19. ↑ Han XY, Sizer KC, Thompson EJ, Kabanja J, Li J, Hu P; et al. (2009). "Comparative sequence analysis of Mycobacterium leprae and the new leprosy-causing Mycobacterium lepromatosis". J Bacteriol. 191 (19): 6067–74. doi:10.1128/JB.00762-09. PMC 2747882. PMID 19633074.
  20. ↑ Walker, Stephen L.; Lockwood, Dina N.J. (2007). "Leprosy". Clinics in Dermatology. 25 (2): 165–172. doi:10.1016/j.clindermatol.2006.05.012. ISSN 0738-081X.
  21. ↑ Ustianowski AP, Lawn SD, Lockwood DN (2006). "Interactions between HIV infection and leprosy: a paradox". Lancet Infect Dis. 6 (6): 350–60. doi:10.1016/S1473-3099(06)70493-5. PMID 16728321.
  22. ↑ 22.0 22.1 Modlin RL, Hofman FM, Taylor CR, Rea TH (1983). "T lymphocyte subsets in the skin lesions of patients with leprosy". J Am Acad Dermatol. 8 (2): 182–9. PMID 6219136.
  23. ↑ Balagon, M. V. F.; Gelber, R. H.; Abalos, R. M.; Cellona, R. V. (2010). "Reactions Following Completion of 1 and 2 Year Multidrug Therapy (MDT)". American Journal of Tropical Medicine and Hygiene. 83 (3): 637–644. doi:10.4269/ajtmh.2010.09-0586. ISSN 0002-9637.
  24. ↑ Wallach D, Flageul B, Bach MA, Cottenot F (1984). "The cellular content of dermal leprous granulomas: an immuno-histological approach". Int J Lepr Other Mycobact Dis. 52 (3): 318–26. PMID 6332791.
  25. ↑ 25.0 25.1 25.2 25.3 25.4 25.5 25.6 25.7 25.8 "Public Health Image Library (PHIL), Centers for Disease Control and Prevention".


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