Carrier detection and prenatal diagnosis in X linked muscular dystrophy using restriction fragment length polymorphisms.

With the aim of offering carrier detection, genetic counselling, and prenatal diagnosis to as many families with Duchenne (DMD) and Becker (BMD) muscular dystrophy as possible, we used available DNA probes to determine the usefulness of the RFLP approach. We report in detail the risks calculated using Bayesian theory and combining pedigree and creatine kinase (CK) data with information derived from the RFLP studies. To date we have analysed members of 28 DMD families (10 familial, 18 sporadic) and six BMD families (four familial, two sporadic) with the closely linked pERT probes 87-1, 87-8, and 87-15 (DXS164). In addition, key members of all families were analysed with probes D2 (DXS43), C7 (DXS28), 754 (DXS84), and L1 X 28 (DXS7). Of the 97 females at risk of being carriers (not including 26 obligate carriers), the RFLP results were compatible with carriership in 22 and not in 51. In 24 females (including 17 mothers of sporadic cases), no information regarding carriership was derived from the RFLP studies. There was no disagreement between pedigree information, clearly raised CK values, and DNA studies. Of 52 obligate or possible carriers under the age of 45, prenatal diagnosis is possible in 49. Prenatal diagnostic RFLP studies have so far been done in three women. In one sporadic DMD family and one BMD family with three affected males the probands showed a deletion involving the three pERT87 subclones used. Experience derived from these families indicates that in our society genetic counselling in X linked muscular dystrophy is received with approval or even enthusiasm in spite of the 5% error estimate that we have quoted for pERT87 derived results.