Albinism pathophysiology: Difference between revisions
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** Monocular vision is manifested as [[strabismus]] | ** Monocular vision is manifested as [[strabismus]] | ||
** In [[albinism]], [[macular]] pigment absent and [[fovea]] [[hypoplasia]] leads to decreased [[visual acuity]] | ** In [[albinism]], [[macular]] pigment absent and [[fovea]] [[hypoplasia]] leads to decreased [[visual acuity]] | ||
** [[Visual acuity]] ranges | ** [[Visual acuity]] ranges froHPS1 gene (HPS1), AP3B1 gene (HPS2), HPS3 gene (HPS3), HPS4 gene (HPS4), HPS5 gene (HPS5), HPS6 gene (HPS6), DTNBP1 gene (HPS7m 20/60 to 20/400 <ref name="pmid20301683"/><ref name="pmid31777350">{{cite journal| author=Marçon CR, Maia M| title=Albinism: epidemiology, genetics, cutaneous characterization, psychosocial factors. | journal=An Bras Dermatol | year= 2019 | volume= 94 | issue= 5 | pages= 503-520 | pmid=31777350 | doi=10.1016/j.abd.2019.09.023 | pmc=6857599 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=31777350 }} </ref><ref name="pmid546241">{{cite journal| author=Witkop CJ| title=Albinism: hematologic-storage disease, susceptibility to skin cancer, and optic neuronal defects shared in all types of oculocutaneous and ocular albinism. | journal=Ala J Med Sci | year= 1979 | volume= 16 | issue= 4 | pages= 327-30 | pmid=546241 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=546241 }} </ref><ref name="pmid3288382">{{cite journal| author=King RA, Summers CG| title=Albinism. | journal=Dermatol Clin | year= 1988 | volume= 6 | issue= 2 | pages= 217-28 | pmid=3288382 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3288382 }} </ref> | ||
===Genetics=== | |||
* [[Genetic mutation]] in [[albinism]] include:<ref name="pmid17980020">{{cite journal| author=Grønskov K, Ek J, Brondum-Nielsen K| title=Oculocutaneous albinism. | journal=Orphanet J Rare Dis | year= 2007 | volume= 2 | issue= | pages= 43 | pmid=17980020 | doi=10.1186/1750-1172-2-43 | pmc=2211462 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17980020 }} </ref><ref> {{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK519018/ |title=Albinism - StatPearls - NCBI Bookshelf |format= |work= |accessdate=}}</ref><ref name="pmid19390472">{{cite journal| author=Summers CG| title=Albinism: classification, clinical characteristics, and recent findings. | journal=Optom Vis Sci | year= 2009 | volume= 86 | issue= 6 | pages= 659-62 | pmid=19390472 | doi=10.1097/OPX.0b013e3181a5254c | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19390472 }} </ref> | |||
** [[Tyrosinase]] in [[OCA1]]; [[autosomal recessive]] | |||
** P protein in [[OCA2]];[[autosomal recessive]] | |||
** [[Tyrosinase-related]] protein 1 ([[TYRP1]])in [[OCA3]]; [[autosomal recessive]] | |||
** [[solute carrier family]] 45, member 2 ([[SLC45A2]]) in [[OCA4]]; [[autosomal recessive]] | |||
** Gene mutation in [[OCA5]] is not identified; [[autosomal recessive]] | |||
** [[SLC24A5]] in [[OCA]]6; [[autosomal recessive]] | |||
** Leucine-rich melanocyte differentiation associated protein ([[LRMDA]]) in [[OCA7]]; [[autosomal recessive]] | |||
** Gene mutation in [[Hermansky-Pudlak syndrome]] ([[HPS]]) subtypes are as following: | |||
*** [[HPS1]], [[AP3B1]], [[HPS3]], [[HPS4]], [[HPS5]], [[HPS6]], [[DTNBP1]]; [[autosomal recessive]] | |||
** [[LYST]] in [[Chediak-Higashi syndrome ]]; [[autosomal recessive]] | |||
** [[GPR143]] in ocular albinism 1; x-linked | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
Revision as of 03:19, 18 August 2021
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Albinism Microchapters |
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Albinism pathophysiology On the Web |
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Risk calculators and risk factors for Albinism pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shadan Mehraban, M.D.[2]
Overview
Pathophysiology
Physiology
- Melanocytes are derived from neural crest ectoderm and are found in hair follicles, skin, eyes, and inner ear
- Melanocytes account for 5% to 10% of cells in epidermal basal layers
- Melanocytes contain melanosomes which produce melanin
- Melanin protects skin from ultraviolet; with sun exposure melanin pigment increases in the skin
- Apart from the photo-protective effect of melanin, it has some roles in the development of ocular structures as well as oculoneural pathways
- Melanin converts tyrosine to 2 forms named eumelanin and pheomelanin
- Eumelanin is responsible for black or brown skin color and protects skin from ultraviolet B
- Pheomelanin is responsible for red or blond hair and light-colored, and ruddy skin
- On melanocytes, activation of melanocortin one receptors (MC1R) lead to synthesis of eumelanin over pheomelanin [1][2]
Pathogenesis
- Mutation in Tyrosinase enzyme is responsible for causing albinism
- Tyrosinase converts tyrosine to DOPA and then dopaquinone; subsequenstly, dopaquionone converts to either eumelanin or pheomelanin
- Tyrosinase mutation is seen in oculocutaneous albinism 1 (OCA1) and autosomal-recessive ocular albinism (AROA)
- Lack of melanin increase chances of sun-damage related diseases including actinic keratosis and UV-related malignancies
- Ocular albinism pathway:
- In uterus, melanin is responsible for developement of the fovea, optic nerves, optic tracts, and visual cortex
- Decussation of some optic nerve fibers at optic chiasm are essential for binocular vision
- In people without albinism, about 45% of optic nerve fibers from the temporal part of retina do not cross the optic chiasem to controlateral lateral geniculate nucleus
- In albinism, most of nerve fibers decussate at optic chiasm and cause monocluar vision
- Monocular vision is manifested as strabismus
- In albinism, macular pigment absent and fovea hypoplasia leads to decreased visual acuity
- Visual acuity ranges froHPS1 gene (HPS1), AP3B1 gene (HPS2), HPS3 gene (HPS3), HPS4 gene (HPS4), HPS5 gene (HPS5), HPS6 gene (HPS6), DTNBP1 gene (HPS7m 20/60 to 20/400 [2][3][4][5]
Genetics
- Genetic mutation in albinism include:[6][7][8]
- Tyrosinase in OCA1; autosomal recessive
- P protein in OCA2;autosomal recessive
- Tyrosinase-related protein 1 (TYRP1)in OCA3; autosomal recessive
- solute carrier family 45, member 2 (SLC45A2) in OCA4; autosomal recessive
- Gene mutation in OCA5 is not identified; autosomal recessive
- SLC24A5 in OCA6; autosomal recessive
- Leucine-rich melanocyte differentiation associated protein (LRMDA) in OCA7; autosomal recessive
- Gene mutation in Hermansky-Pudlak syndrome (HPS) subtypes are as following:
- LYST in Chediak-Higashi syndrome ; autosomal recessive
- GPR143 in ocular albinism 1; x-linked
References
- ↑ "Albinism - StatPearls - NCBI Bookshelf".
- ↑ 2.0 2.1 Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Mirzaa G; et al. (1993). "GeneReviews®". PMID 20301683.
- ↑ Marçon CR, Maia M (2019). "Albinism: epidemiology, genetics, cutaneous characterization, psychosocial factors". An Bras Dermatol. 94 (5): 503–520. doi:10.1016/j.abd.2019.09.023. PMC 6857599 Check
|pmc=value (help). PMID 31777350. - ↑ Witkop CJ (1979). "Albinism: hematologic-storage disease, susceptibility to skin cancer, and optic neuronal defects shared in all types of oculocutaneous and ocular albinism". Ala J Med Sci. 16 (4): 327–30. PMID 546241.
- ↑ King RA, Summers CG (1988). "Albinism". Dermatol Clin. 6 (2): 217–28. PMID 3288382.
- ↑ Grønskov K, Ek J, Brondum-Nielsen K (2007). "Oculocutaneous albinism". Orphanet J Rare Dis. 2: 43. doi:10.1186/1750-1172-2-43. PMC 2211462. PMID 17980020.
- ↑ "Albinism - StatPearls - NCBI Bookshelf".
- ↑ Summers CG (2009). "Albinism: classification, clinical characteristics, and recent findings". Optom Vis Sci. 86 (6): 659–62. doi:10.1097/OPX.0b013e3181a5254c. PMID 19390472.