[The importance of molecular genetic diagnosis of Martin-Bell disease in genetic counseling].

The female consultant had two mentally retarded boys from her two marriages. The clinical symptoms and Fra-X chromosomes indicated their Martin-Bell disease. The daughter of the consultant is healthy and Fra-X negative. She is pregnant and insisted on her molecular genetic diagnosis due to an international collaboration. Both affected brothers had FRAXA genes with a full mutation including more than 200 CGG methylated repeats. The consultant female was in the phase of premutation, however, her healthy daughter had two normal 50% methylated genes with 19 and 26 CGG repeats. Thus there is no recurrence risk for Martin-Bell disease in her fetus.