Type 1 Oculocutaneous albinism (tyrosinase negative)
Oculocutaneous albinism (OCA) is a group of rare genetic disorders affecting the pigmentation system of the skin, hair follicles and eyes. OCA type 1 (OCA1) or tyrosinase negative is caused by mutations in the gene coding for the enzyme tyrosinase, which is involved in melanin synthesis. Melanin, in addition to coloring the skin, hair and eyes, has a protective function against ultraviolet ionizing radiation.
The worldwide incidence of oculocutaneous albinism is 1 in 17,000 individuals, although it may vary between populations. The Cuna Indians (in Panama and Colombia) have the highest reported incidence, which is approximately 6 cases per 1000 inhabitants.
Symptoms
OCA1 causes cutaneous, capillary and ocular hypopigmentation which can be severe or moderate. The most severe form presents with a complete absence of melanin (subtype OCA1A) while in the moderate form there is some accumulation of pigment in the skin and eyes over time (subtype OCA1B). Notable features include:
- Eyes: semi-closed with squinting, photophobia, nystagmus, translucent irises, decreased visual acuity, reduced retinal pigment and strabismus.
- Skin: snow white
- Hair: white
Disease management
Medical follow-up should be performed from birth and throughout the patient's life (pediatricians in childhood and annual check-ups with dermatologists and ophthalmologists). People with OCA1 are more susceptible to sunburn and skin cancer, so they should protect themselves from sun exposure, especially at those times when it is more intense, as well as wearing clothes and glasses with special protective filters.
Genes analyzed
Bibliography
Chan HW, Schiff ER, Tailor VK, et al . Prospective Study of the Phenotypic and Mutational Spectrum of Ocular Albinism and Oculocutaneous Albinism. Genes (Basel). 2021 Mar 30;12(4):508.
Gargiulo A, Testa F, Rossi S, et al . Molecular and clinical characterization of albinism in a large cohort of Italian patients. Invest Ophthalmol Vis Sci. 2011 Mar 14;52(3):1281-9.
Ko JM, Yang JA, Jeong SY, Kim HJ. Mutation spectrum of the TYR and SLC45A2 genes in patients with oculocutaneous albinism. Mol Med Rep. 2012 Apr;5(4):943-8.
Marçon CR, Maia M . Albinism: epidemiology, genetics, cutaneous characterization, psychosocial factors. An Bras Dermatol. 2019 Sep-Oct;94(5):503-520.
Rayner JE, Duffy DL, Smit DJet al . Germline and somatic albinism variants in amelanotic/hypomelanotic melanoma: Increased carriage of TYR and OCA2 variants. PLoS One. 2020 Sep 23;15(9):e0238529.
