Albinism pathophysiology: Difference between revisions
Jump to navigation
Jump to search
| Line 21: | Line 21: | ||
* [[Tyrosinase]] mutation is seen in [[oculocutaneous albinism]] 1 ([[OCA1]]) and [[autosomal-recessive]] [[ocular albinism]] ([[AROA]]) | * [[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]] | * Lack of [[melanin]] increase chances of sun-damage related diseases including [[actinic keratosis]] and UV-related [[malignancies]] | ||
* Ocular albinism pathway: | * [[Ocular]] [[albinism]] pathway: | ||
** In [[uterus]], [[melanin]] is responsible for developement of the [[fovea]], [[optic nerves]], [[optic tracts]], and [[visual cortex]] | ** 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 chiasem]] are essential for binocular vision | ** Decussation of some optic nerve fibers at [[optic chiasem]] 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 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 chiasem and cause monocluar vision | ** In [[albinism]], most of [[nerve fibers]] decussate at [[optic chiasem]] and cause monocluar vision | ||
** Monocular vision is manifested as strabismus | ** Monocular vision is manifested as [[strabismus]] | ||
** In albinism, | ** In [[albinism]], [[macular]] pigment absent and [[fovea]] [[hypoplasia]] leads to decreased [[visual acuity]] | ||
** Visual acuity ranges from 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> | ** [[Visual acuity]] ranges from 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> | ||
==References== | ==References== | ||
Revision as of 02:51, 18 August 2021
|
Albinism Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Albinism pathophysiology On the Web |
|
American Roentgen Ray Society Images of Albinism pathophysiology |
|
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 chiasem 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 chiasem 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 from 20/60 to 20/400 [2][3][4][5]
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.