Oculocutaneous albinism (OCA) is caused by a deficiency of melanin synthesis and characterized by generalized hypopigmentation of skin, hair, and eyes. Due to the hypopigmentation of the retinal pigment epithelium, OCA is usually associated with congenital visual impairment, in addition to an increased risk of skin cancer. OCA is a genetically heterogeneous disease with distinct types resulting from mutations in different genes involved in the pathway which results in pigmentation. OCA1 is associated with mutations in the TYR gene encoding tyrosinase. OCA2 results from mutations in the P gene encoding the P protein and is the most common form of OCA. OCA3, also known as rufous/red albinism, is caused by mutations in the TYRP1 gene, which encodes the tyrosinase‐related protein 1. Recently, OCA4 was described as a new form of OCA in a single patient with a splice site mutation in the MATP gene (or AIM1), the human ortholog of the murine underwhite gene. The similarity of MATP to transporter proteins suggests its involvement in transport functions, although its actual substrate is still unclear. We screened 176 German patients with albinism for mutations within the MATP gene and identified five individuals with OCA4. In this first report on West European patients, we describe 10 so far unpublished mutations, as well as two intronic variations, in addition to two known polymorphisms. Hum Mutat 23:106–110, 2004.

Purpose. To determine whether the size and configuration of the optic chiasm in humans with albinism is different from that in normal control subjects. methods. Seventeen patients and 15 control subjects underwent magnetic resonance imaging of the entire head. Images were reformatted to the chiasm region and analyzed with observer-independent morphometry and measurements by a blinded observer. results. The albino group showed significantly smaller chiasmatic widths, smaller optic nerves and tracts, and wider angles between nerves and tracts. Statistical morphometry showed a different configuration of the optic chiasm. conclusions. Size and configuration of the optic chiasm in humans with albinism are distinctly different from those in normal control subjects and reflect the atypical crossing of optic fibers.