Histopathologic progression and a novel mutation in a child with nemaline myopathy.

Nemaline myopathy is a clinically heterogeneous congenital myopathy caused by mutations in at least 6 genes related to thin filaments. Histologically, they show a characteristic if not homogeneous picture of nemaline rods, essential for the diagnosis. However, little is known regarding the development and progression of muscle histopathologic changes in nemaline myopathy. Results of muscle biopsies at 7 weeks of age and at 15 months of age from a child with nemaline myopathy due to a novel mutation in the ACTA1 gene are presented. The findings of the biopsies, separated by 13 months, demonstrate progression from vague cytoplasmic bodies in the first biopsy to typical nemaline rods in the second biopsy.