[Familial occurrence of a type 2 segmental manifestation of cutaneous leiomyomatosis].

BACKGROUND

There are several malignant or benign skin diseases which can be explained by the phenomenon of mosaicism or segmental manifestation, e. g. segmental neurofibromatosis 1 or cutaneous leiomyomatosis. Loss of heterozygosity is a crucial element for segmental manifestations. Two types of segmental manifestations can be defined in autosomal dominant skin diseases such as cutaneous leiomyomatosis. Type 1 is caused by a novel postzygotic segmental mutation; type 2 reflects an additional postzygotic loss of heterozygosity of the gene locus responsible for cutaneous leiomyomatosis in a initially heterozygous embryo. Loss of heterozygosity is a genetic process when a heterozygous cell becomes homozygous or hemizygous by loosing the corresponding wild-type allele. This phenomenon can be regarded as a precondition for tumor growth. In type-2 cases, the segmental manifestation is more distinctive with additional disseminated disease because of a germline mutation with heterozygosity of all somatic cells outside the strongly affected area.

PATIENTS AND METHODS

A 74-year-old female patient and her 52-year-old son presented with segmental leiomyomas following the lines of Blaschko as well as disseminated skin tumors. The woman has undergone hysterectomy at the age of 29 because of multiple uterine leiomyomas, as had her mother and grandmother.

RESULTS

Based on their typical clinical appearance, these cases represent the rare familial occurrence of type-2 manifestation of leiomyomas which indicates a postzygotic loss of the wild-type allele.

CONCLUSION

Very unusual is the familial occurrence in mother and son of this type-2 manifestation of cutaneous leiomyomatosis. Apparently the gene locus is prone to a postzygotic loss of heterozygosity.