See Tripathi et al. (1992) for the GGC(gly)-to-GAC(asp) mutation at codon 47. Oetting et al. (1993) found this mutation to be frequent among albinos in Puerto Rico. They found the G47D mutation in homozygous state in 9 of 12 unrelated Puerto Ricans with type IA oculocutaneous albinism (OCA1A; 203100). Two other individuals were heterozygous for the mutation; 1 of these had the T373K mutation (606933.0003) in the homologous allele. One of the individuals with Negroid features was homozygous for a W236X mutation (606933.0035). Because of the migration between Puerto Rico and the Canary Islands, 3 persons with OCA from the Canary Islands were analyzed. One was a genetic compound for the G47D mutation and a novel L216M mutation (606933.0036), one was homozygous for the P81L mutation (606933.0002), and one was heterozygous for the P81L mutation. Haplotype analysis in the Puerto Rican cases showed that the G47D mutation occurred on a single haplotype, consistent with a common ancestor for all individuals having this mutation. Two different haplotypes were found associated with the P81L mutation, suggesting that this may be either a recurring mutation for the tyrosinase gene or a recombination between haplotypes.
Chiang et al. (2008) reported a Hispanic family in which 2 sibs had variable manifestations of OCA1B (606952). A 6-year-old boy had nystagmus, decreased vision, light hair, light skin color, and foveal hypoplasia. His sister had exotropia, blonde hair, light skin color, and brown irides with no history of nystagmus, foveal hypoplasia or decreased vision. Genetic analysis identified compound heterozygosity for 2 variants in the TYR gene: G47D and the hypomorphic allele R402Q (606933.0009). Each unaffected parent was heterozygous for 1 of the variants. Chiang et al. (2008) postulated that the clinical spectrum of OCA depends on a pigmentation threshold of the affected individual, and that OCA is a quantitative trait disorder with phenotypic variation in individuals of different ethnic backgrounds.
