Albinism

Abstract Albinism covers a spectrum of inherited hypopigmentation disorders characterized by the reduction or total absence of pigment from the eye, hair, and skin. Most cases of albinism are inherited in an autosomal recessive fashion, but some are inherited in an X-linked or autosomal dominant manner. Even as the molecular genetic understanding of pigmentation disorders has improved, no relevant genotype-phenotype correlation has been found. Albinism results from the defective production of melanin from tyrosine through a complex pathway of metabolic reactions involving enzymes and proteins coded for by genes on several chromosomes. The most accurate classification of disorders featuring albinism is based on specific genetic defects rather than clinical features. The ocular findings in all forms of albinism are consistent, though variable in severity and number in the individual patient. Clinical signs include nystagmus, hypopigmentation of the uveal tract, and retinal pigment epithelium, resulting in iris transillumination defects and fundus hypopigmentation, foveal hypoplasia, optic nerve anomalies, and abnormal decussation of optic nerve fibers at the chiasm. Strabismus and refractive errors are common. Symptoms include decreased best-corrected visual acuity, reduced or absent stereo acuity, compensatory head postures, and photophobia.