No abstract

A case report is given of a pair of monozygotic twin girls with neurofibromatosis caused by a new mutation. The symptomatology was dominated by a neurofibrosarcoma on the leg of one twin and by a large plexiform neurofibroma on the neck of the other twin. Otherwise, the disease showed similar, although not identical or mirror-image distribution of subcutaneous neurofibromas and café-au-lait spots. The twins had identical HLA and blood group antigens and the same chromosome aberration. These case reports indicate that nonhereditary factors may influence the manifestations of neurofibromatosis. A review of the literature on monozygotic twins with neurofibromatosis is given.

The epidemiology and genetics of neurofibromatosis were described in a previously published population study. The present paper supplements that investigation with an estimation of mutation rate and relative fertility, or selection disadvantage, of neurofibromatosis. The relative fertility was estimated to be 78 % and the mutation rate was found to be somewhere between 2.4 and 4.3xThe results verify that this common disease has one of the highest mutation frequencies known in man.Hans Olof Akesson, Department of Psychiatry 111, LiNhagen Hospital, S-422 03 Hisings Backa, Sweden