BRIEF CLINICAL REPORT - PRENATAL-DIAGNOSIS OF CONGENITAL MYOTONIC-DYSTROPHY AND COUNSELING OF THE PREGNANT MOTHER - CASE-REPORT AND LITERATURE-REVIEW

The molecular basis of the myotonic dystrophy (MD) kinase gene is expa nsion of the CTG repeat at the 3'-untranslated region of the MD gene. Variability of the CTG repeat size in different tissues of affected in dividuals has been demonstrated, The objective of this report was to e xamine and review the feasibility of prenatal diagnosis of congenital myotonic dystrophy (CMD) in pregnant women with MD using CTG; repeat s izes in amniocytes or villi. We present a case of a pregnant woman wit h MD who underwent prenatal diagnosis of MD using amniocytes. The repe at size in the amniocytes was smaller than the repeat size in the mate rnal leukocytes and smaller than the repeat size in the infant blood. The infant had CMD. We also reviewed the literature for reports on MD cases that were prenatally tested for CTC; repeat size using amniocyte s or chorionic villi. Data were tabulated based on the number of mater nal CTG repeats, prenatal procedure [amniocentesis or chorionic villus sampling (CVS)], CTC; repeat size in fetal tissue, fetal/infant blood , and pregnancy outcome. Twenty-seven pregnancies at risk for MD that underwent prenatal diagnosis were reported. Eleven (40.7%) of the 27 p regnancies underwent amniocentesis, and 16 (59.3%) underwent CVS. Four teen patients (61%) demonstrated an increase in CTG repeat size in the amniocytes or villi compared with the maternal repeat size. Nine (33% ) of the 27 pregnancies were terminated because of CMD risk. The outco mes of 11 (40.7%) pregnancies were consistent with diagnosis of CMD, C MD was diagnosed in fetuses demonstrating expansion or contraction of the CTG mutation in the amniocytes. Prenatal diagnosis of MD is possib le by using mutation analysis on maternal and fetal DNA and detection of the CTG repeat expansion. Prenatal diagnosis of CMD is more complex . The possible lack of correlation between CTG repeat size in amniocyt es, villi, and other fetal tissues is a potential limitation in prenat al diagnosis and counseling of CMD using CTC; repeat size. Thus, prena tal diagnosis of CMD should be based on a combination of factors, incl uding maternal pregnancy history, clinical findings, and cautious inte rpretation of maternal and fetal DNA analysis. (C) 1998 Wiley-Liss, In c.