Early infant death in nemaline (rod) myopathy.

Congenital 'floppy infant' syndrome with very early death is uncommon. It is here described in a girl. Histopathological examination of a muscle biopsy at the age of 10 days showed rods and infiltration of inflammatory cells. Death occurred at 5 weeks of age. Electron microscopy of the necropsy material showed widened Z disks and rods of Z disk density with a typical transverse periodicity of 18-20 nm. The differential diagnosis between nemaline (rod) myopathy and infantile polymyositis is discussed. Nemaline (rod) myopathy should always be considered in cases of the congenital 'floppy infant' syndrome.