Genetics of seven Dutch familial atypical multiple mole-melanoma syndrome families: a review of linkage results including chromosomes 1 and 9.

Familial atypical multiple mole-melanoma syndrome is characterized by the familial occurrence of malignant melanoma of the skin in combination with multiple atypical precursor nevi; its pattern shows a dominant inheritance in pedigrees. During the last 5 years we have performed linkage analysis in seven Dutch familial atypical multiple mole-melanoma families to define the locus of the underlying gene defect. In 1989 it was reported that in familial melanoma families in the USA a disease-gene was located on chromosome 1p. However, in the Dutch families we could exclude this chromosome from harboring the Dutch familial atypical multiple mole-melanoma gene. Very recently a new candidate locus was found on chromosome 9p, which could be confirmed in our family material. A melanoma-associated gene was linked to several markers on chromosome 9p21. In a linkage analysis in which only melanoma patients were considered as affected, marker D9S171 showed a maximum lod score of 3.11 (theta 0.0). After introducing family members with 10 or more, or five or more, atypical nevi as affected in addition to the melanoma patients, the maximum lod score rose to 4.88 (theta 0.05) and 3.79 (theta 0.07), respectively. Interestingly, the sharing of a unique chromosome 9p21 haplotype among most melanoma patients in the families from two different villages suggests that an old common mutation is present in the Leiden region.