Albinism, Oculocutaneous, Type Iv

A number sign (#) is used with this entry because oculocutaneous albinism type IV (OCA4) is caused by homozygous or compound heterozygous mutation in the MATP gene (SLC45A2; 606202) on chromosome 5p13.

For a general phenotypic description and a discussion of genetic heterogeneity of oculocutaneous albinism, see OCA1 (203100).

Clinical Features

Newton et al. (2001) reported a Turkish patient with generalized hypopigmentation and ocular abnormalities consistent with OCA. He had white hair, pale skin, and translucent blue-gray irides. The phenotype was reminiscent of the relatively mild OCA2 (203200).

Inagaki et al. (2004) reported Japanese patients with OCA4. Hair color ranged from white to yellow to brown, and iris color ranged from blue to brown. Most patients had nystagmus.

Rundshagen et al. (2004) reported 5 unrelated German patients with OCA4. Clinical features included lack of pigmentation of the skin, hair, and eyes associated with classic albinism ocular abnormalities, including decreased visual acuity, macular hypoplasia, optic dysplasia, atypical choroidal vessels, and nystagmus. Most patients did not show increased pigmentation with age or ability to tan.

Molecular Genetics

Newton et al. (2001) identified a homozygous mutation in the SLC45A2 gene (606202.0001) in a Turkish patient with OCA4. The patient's parents were heterozygous for the mutation.

Rundshagen et al. (2004) screened 176 German patients with albinism for mutations in the MATP gene; in 5, they identified homozygous or compound heterozygous mutations (see 606202.0002-606202.0005). These 5 patients were considered to be affected by OCA4.

In 18 of 75 (24%) unrelated Japanese patients with OCA, Inagaki et al. (2004) identified 7 mutations in the MATP gene (see, e.g., D157N, 606202.0006). The authors suggested that OCA4 is one of the most common types of albinism in Japan.

Inagaki et al. (2005) investigated the haplotypes of 20 alleles carrying the D157N mutation from 1 Korean and 21 Japanese OCA4 patients and found 1 Korean and 12 Japanese alleles to be associated with so-called 'haplotype 15' (G-A-G-A-G). Their results were consistent with a founder effect for the D157N mutation in East Asia, suggesting that Japan and Korea might be areas with a high prevalence of OCA4. Inagaki et al. (2005) suggested that the D157N mutation might have occurred on an ancestral chromosome after the divergence of East Asians and Caucasians approximately 15,000 to 35,000 years ago.