"Shake hands"; diagnosing a floppy infant--myotonic dystrophy and the congenital subtype: a difficult perinatal diagnosis.

Myotonic dystrophy is a multi-organ disease inherited in a complicated way. Congenital myotonic dystrophy is a distinct entity with severe symptoms leading to a high rate of perinatal morbidity and mortality. The occurrence of congenital myotonic dystrophy often allows a subsequent diagnosis in the mother with important implications for her life, her further pregnancies and offspring. Genetic principles of anticipation and somatic mosaicism are involved and hamper the prenatal diagnostic possibilities. A family is presented in which maternal myotonic dystrophy and congenital myotonic dystrophy were diagnosed after the third pregnancy. The key features leading to the diagnosis were obstetric history, neonatal hypotonia and asphyxia, facial abnormalities in the mother together with the inability to bury eyelashes and delayed release of grip after shaking hands. The disorder is reviewed with respect to clinical symptoms, pathogenesis and genetics.