PURPOSE: The purpose of this study is to describe the heterogeneous phenotype of 
individuals with an unusual type of albinism--minimal pigment oculocutaneous 
albinism.
METHODS: Nine patients with minimal pigment oculocutaneous albinism were 
identified and followed for up to 11 years. The criteria were the presence of 
oculocutaneous albinism in association with low hairbulb tyrosinase activity in 
the patient and disparate activity in the parents with one parent having normal 
activity and the other having low tyrosinase activity. Changes in skin, hair, 
and ocular pigment were followed as the patients matured. As a measure of ocular 
pigment, iris transillumination and macular transparency were graded according 
to a previously published scheme.
RESULTS: Patients were born with white scalp hair and skin, and nystagmus 
developed. Visual acuity was reduced to 20/50 to 20/200 for the group, but in 
one patient vision improved with maturity. Irides were blue. In seven patients, 
iris pigment developed, which was detected by transillumination with slit-lamp 
biomicroscopy, including the one patient with improved visual acuity. All 
patients had foveal hypoplasia, and melanin pigment in the fundi could not be 
detected by clinical examination. Visual acuity in the group did not correlate 
directly with the presence or development of iris transillumination or macular 
transparency. The pedigrees were consistent with an autosomal recessive 
inheritance pattern.
CONCLUSION: This unique type of oculocutaneous albinism has heterogeneous 
clinical features. Minimal pigment oculocutaneous albinism appears to represent 
a new type of tyrosinase-related oculocutaneous albinism (OCA1MP).