Prenatal diagnosis of oculocutaneous albinism type I: Review and personal experience

Oculocutaneous albinism type I(OCA I) comprises autosomal recessive syndrom es of hypopigmentation and low vision, caused by the lack of tyrosinase act ivity. Affected families seek genetic counseling and prenatal diagnosis as preventive measures. Until recently, prenatal diagnosis of OCA I was achiev ed by histologic and electron microscopic examination of fetal skin biopsie s. Lately, a molecular genetic approach has become possible by the identifi cation of the two mutated copies of the TYR gene, coding the tyrosinase, in which over 60 mutations have been identified. We report here our experience in prenatal diagnosis of OCA I using the two strategies. Thirty-four prenatal tests were performed in fetuses at risk fo r OCA I. In 31 cases the diagnosis was made in fetal scalp biopsies using t he histological approach. The microscopic observations revealed normal mela nogenesis in 26 biopsies. Five albino fetuses were diagnosed by the demonst ration of arrest of melanogenesis in early stages I and II. In three pregna ncies, molecular genetic tests were per formed on DNA extracted from amnioc ytes, using direct mutation analysis (in one), and complemented by linkage analysis (in two). One albino and two normally pigmented fetuses were diagn osed. The prenatal molecular genetic test can be applied to families when at leas t one mutation is diagnosed in the albino patient. The histological approac h is applicable in all families at risk for OCA I.