Congenital Myotonic Dystrophy
Myotonic dystrophy is transmitted as an autosomal dominant trait. Nevertheless, only if the mother has the disease will a neonate show signs of it .

Figure 143.1.— Neonate with myotonic dystrophy. Generalized hypotonia with myopathic facies.

Congenital myotonic dystrophy is a disease that affects the brain and the muscles. Neonates with congenital myotonic dystrophy are usually hypotonic at birth or become hypotonic shortly after birth. The patient presents with generalized hypotonia with decreased dynamic tone, weakness, facial diplegia, and feeding difficulty (masticatory and pharyngeal muscle weakness). Constipation may be present. Clinical myotonia is seldom present in the neonatal period. Weakness in the neonatal period is more proximal than distal. Arthrogryposis is often present. A history of polyhydramnios is common. Clues to the prenatal onset of motor dysfunction are: (1) undecended testicles, a sign of dysfunction of the gubernaculum; (2) inverted V-shaped mouth, high arch palate and dysmorphic ears, signs of facial muscles dysfunction; and (3) slender ribs indicate weakness of the intercostal muscles. Cataracts may be presents (Figure 143.2).

Figure 143.2.— Neonate with myotonic dystrophy. Cataract noted shortly after birth.

Chest radiograph shows slender ribs. MRI of the brain may show large ventricles with colpocephaly.