Albinism

Inheriting altered copies of at least 12 different genes that do not work properly is the cause of most types of albinism. About 20% of individuals with albinism remain molecularly unresolved in all genetic diagnosis centers due to the mutation status in known genes. Hypopigmentation, white blood cell abnormalities, short lifespan, eye diseases, and skin diseases are seen. It is an inherited disease that can be transmitted both as an autosomal recessive inheritance and X-linked, depending on the type. There are 2 types of albinism:

  • Oculocutaneous albinism (OCA)
  • Ocular albinism (OA)

OCA is the most common and only autosomal recessive type. It affects the skin, hair, and eyes. OA, on the other hand, is the rarer type and in addition to autosomal recessive transmission, some types can also be X-linked. Mainly affects the eyes1,2,3.

Gene Chromosomal locationa Albinism typeb OMIMc ORPHANETd HGNCe
TYR 11q14.3 OCA1f #203100 ORPHA352731 HGNC:12442
OCA2 15q12-q13.1 OCA2 #203200 ORPHA79432 HGNC:8101
TYRP1 9p23 OCA3 #203290 ORPHA79433 HGNC:12450
SLC45A2 5p13.2 OCA4 #696574 ORPHA79435 HGNC:16472
n.d. 4q24 OCA5 #615312 n.d. HGNC:44139
SLC24A5 15q21.1 OCA6 #609802 n.d. HGNC:20611
C10orf11 10q22.2-q22.3 OCA7 #615179 ORPHA352745 HGNC:23405
GPR143 Xp22.2 OA1 #300500 ORPHA54 HGNC:20145
LYST 1q42.3 CHS1 #214500 ORPHA167 HGNC:1968
HPS1 10q24.2 HPS1 #203300 ORPHA231500 HGNC:5163
AP3B1 5q14.1 HPS2 #608233 ORPHA183678 HGNC:566
HPS3 3q24 HPS3 #614072 ORPHA231512 HGNC:15597
HPS4 22q12.1 HPS4 #614073 ORPHA231500 HGNC:15844
HPS5 11p15.1 HPS5 #614074 ORPHA231512 HGNC:17022
HPS6 10q24.32 HPS6 #614075 ORPHA231512 HGNC:18817
DTNBP1 6p22.3 HPS7 #614076 ORPHA231531 HGNC:17328
BLOC1S3 19q13.32 HPS8 #614077 ORPHA231537 HGNC:20914
BLOC1S6 15q21.1 HPS9 #614171 ORPHA280663 HGNC:8549

Table: Human genes related to albinism. OCA2 is the most common form worldwide4.

In addition to having different causes, they can also have different symptoms. In Hermansky-Pudlak syndrome, there are symptoms similar to OCA, but intestinal, heart, kidney, and lung diseases or hemophilia are more likely, while in Chediak-Higashi syndrome, a person’s hair may appear silvery and their skin may appear slightly gray. Infection is more likely as there may be defects in the white blood cells. The reasons for the different types are also different. For example, with a mutation in the OCA1 tyrosinase gene; OCA2 with a mutation in the OCA2 gene; by mutation of OCA3 tyrosinase-associated protein; OCA4 is caused by mutations in the membrane-associated carrier protein gene8,9,10.

Figure 1: Young Senegalese child with oculocutaneous (a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes) albinism and his mother.

About one in 17,000 people suffer from albinism. They have hypersensitivity to the sun, susceptibility to skin cancer, and retinal abnormalities. Possible eye problems linked to albinism include:

Some retinal abnormalities may occur due to little or no melanin. The reason is that melanin plays an important role in the development of the retina. Possible eye problems of people with albinism are poor vision, astigmatism, photophobia, nystagmus, and strabismus4,5.

Diagnosis

The remarkable features of these patients, whose symptoms can be seen in all races and ages, are that their hair, eyelashes, and skin are white. The irises are light blue-pink, but completely translucent. In addition to being a visible disease, electrodiagnostic tests are also used to diagnose albinism. In these tests, electrodes are attached to the skin to check the connection between the eye and the part of the brain that controls vision3,6,7.

Figure 2: Eyes of a patient with OCA1A.

Conclusion

People with albinism have different symptoms and severity depending on the mutation location. There is no cure, but it is very important for the person needs to protect himself, especially against the sun. In addition, they lead their lives like other people and there is no condition that affects their intelligence3.

References:

  1. Increasing the complexity: new genes and new types of albinism https://onlinelibrary.wiley.com/doi/10.1111/pcmr.12167# 09.12.2022 / 16.30
  2. Albinism https://www.sciencedirect.com/science/article/pii/B9780123735539000067 09.12.2022 / 17.00
  3. Albinism https://www.nhs.uk/conditions/albinism/ 09.12.2022 / 17.30
  4. Oculocutaneous albinism Grønskov, K., Ek, J. & Brondum-Nielsen, K. Okülokutanöz albinizm. Orphanet J Rare Dis 2 , 43 (2007). 10.12.2022 / 20.15
  5. Oculocutaneous albinism Wei, A.H., Zang, D.J., Zhang, Z. et al. (2013b). Exome sequencing identifies SLC24A5 as a candidate gene for nonsyndromic oculocutaneous albinism. J. Invest. Dermatol. 133, 1834–1840. 10.12.2022 / 21.55
  6. Oculocutaneous albinism Witkop CJ: Albinizm: hematolojik depo hastalığı, cilt kanserine duyarlılık ve her türlü okülokütanöz ve oküler albinizmde paylaşılan optik nöronal defektler. Ala J Med Sci. 1979, 16: 327-330. 10.12.2022 / 21.20
  7. Albinism Kral RA, Summers CG: Albinizm. Dermatol Clin. 1988, 6: 217-228. 11.12.2022 / 12.40
  8. Oculocutaneous albinism Newton JM, Cohen-Barak O, Hagiwara N, Gardner JM, Davisson MT, King RA, Brilliant MH: Mutations in the human orthologue of the mouse underwhite gene (uw) underlie a new form of oculocutaneous albinism, OCA4. Am J Hum Genet. 2001, 69: 981-988. 10.1086/324340. 11.12.2022 / 13.20
  9. Mutation for albinism Boissy RE, Zhao H, Oetting WS, Austin LM, Wildenberg SC, Boissy YL, Zhao Y, Sturm RA, Hearing VJ, King RA, Nordlund JJ: Mutation in and lack of expression of tyrosinase-related protein-1 (TRP-1) in melanocytes from an individual with brown oculocutaneous albinism: a new subtype of albinism classified as “OCA3”. Am J Hum Genet. 1996, 58: 1145-1156. 11.12.2022 / 13.45
  10. Different types of albinism Rinchik EM, Bultman SJ, Horsthemke B, Lee ST, Strunk KM, Spritz RA, Avidano KM, Jong MT, Nicholls RD: A gene for the mouse pink-eyed dilution locus and for human type II oculocutaneous albinism. Nature. 1993, 361: 72-76. 10.1038/361072a0. 11.12.2022 / 14.00

Figure References:

  1. https://onlinelibrary.wiley.com/doi/10.1111/pcmr.12167# 11.12.2022 / 14.30
  2. https://ojrd.biomedcentral.com/articles/10.1186/1750-1172-2-43#Tab1 11.12.2022 / 13.40

Inspector: Nadir KERESTECİ

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