Nemaline Myopathy
Nemaline myopathy, also referred to as rod body myopathy, represents a varied group of disorders with different modes of inheritance, but the most typical form is autosomal recessive.
While the rods may be easily overlooked on routine hematoxylin-and-eosin (H&E) staining, they can be rarely demonstrated with the Gomori trichrome stain. The rods are readily demonstrated on electron microscopy. They are thought to be an abnormal deposition of Z-band material of a protein nature and possibly alpha-actinin. The disease has been linked to at least seven distinct genes. The severe congenital form has been linked to α-Actin, nebulin, and troponin T1 mutations. A milder childhood form has been linked to α-actin, nebulin, α-tropomyosin 3 (TPM3), and β-tropomyosin (TPM2) mutations.A severe form of the disease may present in the neonatal period with severe weakness, respiratory insufficiency, and often a fatal outcome. Most cases present with a mild, nonprogressive myopathy with hypotonia and proximal weakness. In more severe cases, swallowing difficulty may be present in the neonatal period. Skeletal abnormalities, such as kyphoscoliosis, pigeon chest, pes cavus feet, high arched palate, tent-shaped mouth, and an unusually long face has been noted. Cardiomyopathy has been described in both severe neonatal and milder forms of the disease. Autosomal-dominant inheritance has been described in a few instances.