Genetik bei okulokutanem Albinismus

Abstract

Albinism comprises a heterogeneous group of nonprogressive genetic disorders characterized by the absence of pigmentation in the skin, hair, and/or eyes. Hypopigmentation or complete lack of pigmentation is caused by an enzyme deficiency involving the production, metabolism, or distribution of melanin. Clinically, oculocutaneous and ocular types, as well as syndromes associated with albinism resulting from mutations in at least 14 genes, are distinguishable. Most frequent is oculocutaneous albinism (OCA), which is subdivided nowadays into four forms, OCA 1-OCA 4. OCA is inherited as an autosomal recessive trait. Clinical differentiation of OCA types is difficult due to the observed range of phenotypic variation. Thus, genetic analysis may be helpful with respect to a precise diagnosis. Sequencing of the four genes associated with OCA detects variations in approximately 60-70% of German patients with albinism. The majority of German patients are affected by OCA 1 resulting from mutations in the gene for tyrosinase, the key enzyme in the synthesis of melanin pigment. Worldwide, OCA2 is the most frequent form of albinism.