Nemaline myopathy is a disease of voluntary muscle that is often nonprogressive. The most common form of the disease is not fatal, although a rare form of the disorder is.
People with nemaline myopathy have moderate weakness in their leg, arm and trunk muscles, accompanied by some mild weakness of the face, tongue and throat muscles. Reflexes are decreased or absent. Affected children often have long, narrow faces with high-arched palates and slender body musculatures. High-arched feet and curvature of the spine are common, and the jaw may also be malformed. The severest form of nemaline myopathy usually appears at birth. Affected children have a marked weakness and a lack of muscle tone. Their respiratory muscles are weak, and death often occurs in the first few years of life due to respiratory failure.
Nemaline means threadlike, and researchers chose this name because of the presence in affected muscle cells of threadlike or rod-shaped material. The significance of these rodlike bodies is still not clear.