Genetic counseling in Becker type X-linked muscular dystrophy. II: Practical considerations.

A frequent problem of genetic counseling in Becker muscular dystrophy (BMD) is the differential diagnosis between BMD and the autosomal recessive benign limb-girdle muscular dystrophy (LGMD) if the pedigree pattern is not typical of X-linkage. In this situation, the a priori probability that a woman and her husband may be heterozygotes for LGMD can be shown to be 80 mu/a (mu = mutation rate in BMD; a = incidence ratio between BMD and LGMD). In addition, the age-corrected serum creatine kinase (CK) values of all female relatives are also important for the risk calculation of a woman being carrier of BMD.