Myotonic dystrophy (Steinert's disease) in the neonate.

Radiological abnormalities of the ribs are reported in 5 newborn infants with myotonic dystrophy. In all 5, the ribs appeared very thin, in contrast to the normal appearance of the rest of the skeleton. This slenderness, which is important for diagnosis and prognosis, seems to be caused by hypotonia of the intercostal muscles. However, it is not pathognomonic of myotonic dystropy, for it can be observed in other myopathies.