Neonatal nemaline myopathy with abundant intranuclear rods

A term hypotonic female infant was born to a primigravida mother. The infant required mechanical ventilation from birth until death at 5 weeks of age. An elevated serum creatine kinase of 1300 IU l-1 lead to a quadriceps muscle biopsy at 3 days of age. The biopsy showed numerous intranuclear inclusions on light microscopy. Electron microscopy revealed the inclusions to be rod (nemaline) bodies and were located in 80% of the muscle nuclei. Cytoplasmic rod bodies were also present in 50% of the muscle fibers, often arising from Z discs. The intranuclear rods were more than ten times larger than the cytoplasmic rods. There have been eight reported cases of abundant intranuclear rods in nemaline myopathy: three adult onset; one childhood onset; and four neonatal (including this case). Six of the cases (all of the neonatal and two adult onset) died due to respiratory failure and pneumonia. While intranuclear rods are unusual in nemaline myopathy, they occur in both adult and neonatal cases, and their presence is often associated with a fatal outcome.