High stature in neonatal myotubular myopathy.

Abstract

A male baby was delivered at 40 weeks of gestation. His birthweight was 3300 g (50th percentile) and length 57 cm (over the 97th percentile). Parents measured 1.70 m and 1.83 m, respectively. The mother later gave birth to two healthy infants, a boy and a girl who measured 53 cm and 47 cm and weighed 3800 g and 2700 g at 40 weeks and 39 weeks of gestation, respectively. In our patients the chest X-ray at birth showed the characteristic thin ribs (Fig. 1). A diagnosis of neuromuscular disease was rapidly made on the basis of persistent generalized hypotonia, muscle atrophy, and feeble respiratory efforts. Muscle biopsies taken from the biceps on the 8th day revealed the characteristic features of myotubular myopathy with predominance of type I fibres and persistence of fetal myotubes in a large proportion of the muscle fibers (Fig. 2). The baby died at 2 months of age from respiratory insufficiency. His mother was clinically normal and her muscle biopsy did not show any abnormality. Because of the high stature observed in this patient, previously published cases of neonatal myotubular myopathy were reviewed and birth length parameters were plotted on Lubchenco growth curves. Only in 6 previously reported cases (14) the height had been recorded. In four of the 6 infants the height was over the 90th percentile, and all had a decreased weight for height (Fig. 3).