Oculocutaneous albinism type 7: Overlap and differences with other types of non-syndromic albinism

Abstract

Abstract Purpose: To expand on the phenotype of oculocutaneous albinism type 7 (OCA7). Patients and Methods: We describe three patients with OCA7: two from a consanguineous family of Kurdish origin and one patient of Dutch origin. We compare them with all patients described to date in the literature. Results: All newly described patients had severely reduced visual acuity (VA), nystagmus, hypopigmentation of the fundus, severe foveal hypoplasia, and chiasmal misrouting. None had iris translucency. All patients had normal pigmentation of skin and hair. We found one novel mutation in the Dutch patient: c.565G>A; p.(Gly189Ser). We compared our patients to the 15 described in the literature to date. All 18 patients had substantially pigmented skin and hair, very poor VA (0.4-1.3 logMAR), nystagmus, (mild) ocular hypopigmentation, foveal hypoplasia, and misrouting. Discussion: Although pigmentation levels are mildly affected in OCA7, patients have a severe ocular phenotype with VA at the poorer end of the albinism spectrum, severe foveal hypoplasia, and chiasmal misrouting. OCA7 patients have a phenotype restricted to the eyes, and similar to that of X-linked ocular albinism. We therefore propose to rename the disorder in ocular albinism type 2. Unfolding the role of LRMDA in OCA7, may bring us a step closer in identifying the responsible factors for the co-occurrence of foveal hypoplasia and misrouting.