Oculocutaneous albinoidism as a manifestation of reduced neural crest derivatives in the Prader-Willi syndrome.

Nine patients with Prader-Willi syndrome (five female and four male; one Oriental and eight white), all of whom had interstitial deletions of the proximal long arm of one chromosome 15 (q11-q13) were found to have decreased tyrosinase activity in isolated hair bulbs. As infants, all patients had light hair and skin coloring, both of which darkened with age. Light and electron microscopic analysis of skin and hair bulbs disclosed a reduced number of melanocytes in the basal epidermis and hair bulbs. Each patient demonstrated decreased pigmentation of the iris stroma, which was accentuated peripherally and manifested clinically as iris translucency. There was no foveal hypoplasia, nystagmus, or photophobia, and ocular function was normal. Oculocutaneous albinoidism is thus a component of del(15q) Prader-Willi syndrome with reduction of melanocytes of neural crest origin (skin, hair, and iris stroma) and retention of normal retinal and iris pigment epithelia of neuroectodermal origin.