CONGENITAL MYOTONIC-DYSTROPHY - MOLECULAR DIAGNOSIS AND CLINICAL-STUDY

Recently, an unstable DNA fragment specific to myotonic dystrophy (MyD ) was discovered. In affected individuals, a DNA fragment is found tha t is larger than in normal siblings. Our objectives were to show wheth er the results of DNA analysis agree with the disease severity and pro gnosis in congenital myotonic dystrophy (CMyD) by DNA analysis. We inv estigated three pregnancies (two studied retrospectively) in three fam ilies. We genotyped the family members with the Southern blots and the polymerase chain reaction (PCR) analysis. In one case a prenatal diag nosis was carried out using chorionic villus sampling. This report als o presents the three cases of affected mothers and CMyD babies with th eir growth courses. We clarify four main problems in CMyD, namely, res piratory distress, delayed motor development, feeding difficulty, and delayed mental development. The allele size in the range of 10 to 13 k b tended to be present as the adult form of MyD, and 14 to 15 kb as th e CMyD. The three CMyD cases whose alleles size in the range of 14 to 15 kb showed various forms of disease and prognosis. We reached the fo llowing conclusions: the disease severity and prognosis in babies with CMyD did not correlate with the result of DNA analysis. The DNA analy sis is a useful test for prenatal diagnosis. However, it is impossible to predict the disease severity and prognosis in babies with CMyD.