FAMILY WITH NEUROFIBROMATOSIS TYPE-2 AND AUTOSOMAL-DOMINANT HEARING-LOSS - IDENTIFICATION OF CARRIERS OF THE MUTATED NF2 GENE

A family is presented in which neurofibromatosis type 2 (NF2) and auto somal dominant hearing loss segregate in an apparently independent way . The presence of the latter condition caused anxiety in all family me mbers at risk for NF2 in whom hearing loss became apparent. Previously , we identified a G --> A transition in the donor splice site of exon 5 of the NF2 gene in a family member with proven NF2. As expected, the mutation was present in two other family members who fulfilled the di agnostic criteria for NF2. Four out of five family members at risk for NF2 developed hearing loss. Two of these had the G --> A transition. The mutation was absent in the two other individuals with hearing loss and in the fifth family member without hearing loss or other clinical symptoms. In this family, the identification of the underlying NF2 ge ne mutation excluded NF2 as the cause of hearing loss in two potential carriers of the mutated gene. On the other hand, it enabled the ident ification of two carriers of the NF2 gene mutation who did not fulfill the diagnostic criteria for NF2. They will have to be monitored very carefully for the development of NF2-associated tumors. The consistent association within this family of a relatively mild clinical phenotyp e with the NF2 mutation, supports earlier suggestions that intrafamili al variability is small in NF2.