Clinical Manifestations and Genetic Spectrum of Oculocutaneous Albinism Type 2 in Chinese Patients.

Objectives

Oculocutaneous albinism (OCA), a group of inherited disorders characterized by deficient melanin synthesis, leads to hypopigmentation of the skin, hair, and eyes. OCA type 2 (OCA2) is caused by mutations in OCA2. This study aimed to characterize the comprehensive clinical and genetic spectrum of OCA2, and to identify the key ocular determinants of visual acuity.

Methods

We enrolled 90 probands clinically diagnosed with albinism. Whole-exome sequencing and comprehensive ophthalmic examinations were performed.

Results

OCA2 was confirmed in 29 probands (32.2%). Visual impairment was distributed as mild/no impairment (30.8%), moderate (53.8%), and severe/blindness (15.4%). All patients exhibited nystagmus and photophobia. Ocular phenotype grading showed distinct distributions: iris translucency (n = 25) was 68% grade 3, 20% grade 2, 8% grade 1, and 4% grade 4; fundus hypopigmentation (n = 26) was 42.3% grade 1, 30.8% grade 2, and 26.9% grade 3; and foveal hypoplasia (n = 20) was 70% grade 4, 25% grade 3, and 5% grade 1. We identified 33 OCA2 variants (26 compound heterozygous and 3 homozygous), with missense variants accounting for 62.1% of alleles. Five variants were identified to be novel. The severity of foveal hypoplasia demonstrated a strong, statistically significant negative correlation with visual acuity (r = -0.71, p < 0.001).

Conclusions

OCA2 accounts for 32.2% of albinism cases, with moderate visual impairment being the most common (53.8%). Graded phenotyping demonstrated moderate-to-severe iris translucency (88%), mild fundus hypopigmentation (42.3%), and severe (grade 4) foveal hypoplasia (70%). The severity of foveal hypoplasia emerged as an important determinant of visual acuity.