A CASE OF PATERNALLY INHERITED CONGENITAL MYOTONIC-DYSTROPHY

We report two sisters with congenital myotonic dystrophy (CDM) born to a normal mother and an affected father. The congenitally affected dau ghters had symptoms from birth. The age of onset of DM in the father w as 39 years. Analysis of the CTG trinucleotide expansion in this famil y showed increase in the repeat length with increasing severity, with the smallest expansion in the grandfather and the largest expansion in the younger of the two CDM sisters. This family shows that exceptiona lly it is possible for CDM to be inherited paternally and refutes the hypothesis that CDM, is exclusively of maternal origin. This contradic ts several of the previous hypotheses concerning the mechanisms by whi ch the CDM phenotype arises.