Genotype-phenotype associations in Danish patients with ocular and oculocutaneous albinism.

ABSTRACT

BACKGROUND: The study aimed to describe genotype-phenotype associations in patients with oculocutaneous and ocular-only albinism and to evaluate a set of diagnostic criteria proposed recently by Kruijt et al. MATERIALS AND METHODS: Genotype-phenotype associations in patients with a clinical diagnosis of albinism were studied based on imaging of hair and ocular features (nystagmus, iris color and translucency, fundus pigmentation and foveal development) and self-evaluated skin type. Patients were sub-grouped based on genetic findings. RESULTS: Patients with biallelic variants in TYR (n = 29), OCA2 (n = 22), other albinism genes (n = 13) or monoallelic variants in GPR143 (n = 13) were included as were 15 patients with a pure clinical diagnosis but no genetic findings. In descending order the most common findings were foveal hypoplasia (any hypoplasia 95.2%, severe 88.0%), nystagmus (93.5%), iris translucency (any translucency 80.2%, moderate to severe 31.5%), misrouting on VEP (80.0%) fundus hypopigmentation (any hypopigmentation 75.8%, severe 30.1%), fair skin type (73.8%), blue irides (62.0%), blonde hair (57.5%), and unpigmented eye lashes (39.1%). There were no phenotypic differences between the different genetic subgroups of albinism but patients with a pathogenic haplotype in TYR in combination with a classic variant had less iris translucency than patients with two classic variants in TYR. CONCLUSIONS: Ocular developmental features were the most common findings whereas phenotypic features related to pigmentation were less common findings but there were no genotype-phenotype correlations. All patients with a genetically confirmed diagnosis of albinism fulfilled the diagnostic criteria by Kruijt irrespective of genetic subtype.