Oculocutaneous albinism (OCA) is manifested by reduced synthesis of melanin, which may result from mutations in a variety of genes. In OCA, hypopigmentation is both cutaneous and ocular, and in the most common types of OCA, other tissues and organs are not significantly involved. Hypopigmentation of the skin is associated with psychological and social problems, decreases natural protection against sunburn, and results in predisposition to skin cancer. In the absence of melanin in the eye, development of the visual pathways is abnormal, resulting in decreased visual acuity, strabismus, nystagmus and photophobia.
One of the most common types of OCA is OCA1, an autosomal recessive disorder of reduced pigmentation in the hair, skin and eyes, resulting from mutations in the tyrosinase gene (TYR), a five exon gene spanning approximately 60 kb on chromosome 11q. Two different types of OCA1, A and B, can be distinguished in humans, based mainly on clinical observation, wherein OCA1A is the more severe type with absence of tyrosinase activity and pigmentation throughout life. The molecular basis of OCA1 is quite heterogeneous, and more than 190 mutations in the TYR gene have been identified so far in different population groups.
Al-Arrayed (Personal communication, Dubai, 2006) indicated that oculocutaneous albinism causes poor vision among some families in Bahrain frequently. However, further studies are needed to determine its prevalence.
Hattab and Amin (2005) described two Jordanian siblings with an association of Papillon Lefevre Syndrome (PLS) and OCA1. The elder brother presented at the age of 20 years with symptoms typical of PLS. Physically, he had snow-white hair, erythema of the face with pustules, and blue-gray irides. He complained of poor visual acuity, photophobia, and showed rotary movements of the eyes. Eye examination revealed lack of retinal pigmentation, prominent choroidal vessels, foveal hypoplasia, and a pale optic disc. . The younger brother was seen at the age of 13 years and presented similar features as his brother's. The parents of these patients were second cousins. However, both the parents as well as two siblings were normal. A younger sister had OCA1. In addition, one brother, also an albino, died at the age of 2-years. A homozygous mutation in the Tyrosine gene was identified in both the patients, as well as their affected sister, while the parents were found to be heterozygous for the mutation. Interestingly, the patients were also found to be homozygous for a mutation in the Cathepsin C (CTSC) gene, located close to the locus for Tyr. The parents were heterozygous for this mutation too.
Hegab (1984) studied 5 female cases of complete ocular albinism and the following clinical manifestations were noted: impaired vision, translucent irides, congenital nystagmus, photophobia, albinotic fundi, undeveloped fovea, complete color vision blindness and straight eyes with no strabismus. [Hegab S. Autosomal dominantly inherited albinism in females: report of five cases. Med J Cairo Univ. 1984; 52(1): 53-8.]
A survey performed by Bastaki et al. (1992) between 1985 and 1989 reported the overall incidence of genodermatosis in Kuwait Maternity Hospital to be 0.26 per 1000 livebirths. More specifically, the incidence of albinism was 0.024 per 1000 livebirths in Kuwait during the over-mentioned period of five years. [Bastaki L, Al-Awadi A, Naguib KK. Incidence of genodermatosis among the neonates in Kuwait Maternity Hospital: 1985 to 1989 survey report, Kuwait Medical Genetics Centre, 1992, Kuwait.]
Zahed et al. (2005) performed ophthalmic and dermatological examinations on 30 Lebanese subjects with OCA, then screened for mutations in the tyrosinase gene in an effort to establish the molecular basis of the disorder in Lebanon.
Rajab et al. (2005) undertook a study to estimate the prevalence of commonly diagnosed autosomal recessive diseases in Oman from a hospital-based register in years 1993 to 2002. The study revealed that oculocutaneous albinism was diagnosed in 14 patients, with an observed incidence of 1 in 30,000 births.
[See: Jordan > Hattab and Amin, 2005].