Two cases of type 2 segmental manifestation in a family with cutaneous leiomyomatosis

Two types of segmental manifestation have been differentiated in autosomal dominant skin disorders. Type 1 reflects heterozygosity for the underlying mutation and the severity of lesions is similar to that observed in the nonmosaic phenotype. Type 2 reflects loss of heterozygosity and the segmental involvement is characterized by a more pronounced manifestation superimposed on the ordinary phenotype. We here describe an unusual familial occurrence of type 2 segmental manifestation of cutaneous leiomyomatosis. The proposita, a 37-year-old woman with a history of multiple uterine leiomyoma, showed multiple agminated firm, pale-red papules arranged in an 8 x 20 cm triangular area on her right chest. A few similar isolated lesions were found to be scattered all over her body. Her 70-year-old mother reported likewise a history of multiple uterine myoma and showed an accumulation of leiomyomas in a band-like area extending from her left chest to the extensor surface of her left forearm. Some isolated nonsegmental lesions were found in other areas of her body. In 1955, one lesion had been surgically removed and histopathological examination showed features of leiomyoma. Moreover, the family history revealed cutaneous leimyomatosis in the proposita's grandmother and in one aunt. Most likely, this familial occurrence of a segmental type 2 manifestation of cutaneous leiomyomatosis in two generations resulted from postzygotic loss of heterozygosity at an early developmental stage. We hypothesize that the underlying gene locus is particularly prone to mitotic recombination or other postzygotic mutational events resulting in loss of the corresponding wild-type allele.