[Familial malignant melanoma].

Approximately 8 to 12% of cases of malignant melanoma (MM) are estimated to be familial in foreign countries, but such familial MM (FMM) is rare in Japan. Eleven Japanese cases of FMM, including our 3 cases in a family, have been reported. Comparison studies have revealed that the mean age at the onset of FMM is younger than that of sporadic MM. However, it is difficult to exclude the effects of early recognition of MM by frequent examinations in FMM families. In the majority of the families, the propensity to MM is associated with the presence of atypical mole, so-called dysplastic nevus syndrome phenotype. The inheritance pattern for FMM is thought to be autosomal dominant with incomplete penetrance. Linkage studies have shown at least two FMM loci on chromosome 1p36 and 9p21, thus providing a support for genetic heterogeneity in FMM.