Sporadic occurrence of Duchenne Muscular Dystrophy: evidence for new mutation

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Abstract
The mechanism of inheritance of sporadically occurring Duchenne muscular dystrophy (DMD) was investigated in 42 families, using carrier detection methods and genetic evaluation. Serum CPK [creatine phosphokinase] detects 72% of female carriers of DMD. Quantitative LDH [lactic dehydrogenase] and/or its isozymes were not a useful means of carrier detection, as previously reported. Employing family pedigree data and CPK carrier testing, the probability that the mother and maternal grandmother in these families were DMD carriers was tested by the Bayesian method. These studies revealed 23 families (Category I) with no evidence for DMD carriers, 11 families (Category II) in which the mother was a carrier and 3 families (CategoryIII) in which mother and maternal grandmother were carriers. Nineteen of the 42 families have a > 83% probability that the sporadic DMD case arose by mutation in a maternal gamete. This finding is in good agreement with the theoretically expected one-third of DMD cases arising by new mutation.