Nemaline myopathy is a disorder that primarily affects skeletal muscles, which are muscles that the body uses for movement. People with nemaline myopathy have muscle weakness (myopathy) throughout the body, but it is typically most severe in the muscles of the face; neck; trunk; and other muscles close to the center of the body (proximal muscles), such as those of the upper arms and legs. This weakness can worsen over time. Affected individuals may have feeding and swallowing difficulties, foot deformities, abnormal curvature of the spine (scoliosis), and joint deformities (contractures). Most people with nemaline myopathy are able to walk, although some affected children may begin walking later than usual. As the condition progresses, some people may require wheelchair assistance. In severe cases, the muscles used for breathing are affected and life-threatening breathing difficulties can occur.
Mutations in one of many genes can cause nemaline myopathy. These genes provide instructions for producing proteins that play important roles in skeletal muscles. Within skeletal muscle cells, these proteins are found in structures called sarcomeres. Sarcomeres are necessary for muscles to tense (contract). Many of the proteins associated with nemaline myopathy interact within the sarcomere to facilitate muscle contraction. When the skeletal muscle cells of people with nemaline myopathy are stained and viewed under a microscope, these cells usually appear abnormal. These abnormal muscle cells contain rod-like structures called nemaline bodies.
Nemaline myopathy has an estimated incidence of 1 in 50,000 individuals.
Nemaline myopathy is usually inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Published Date: December 01, 2015Published By: National Institutes of Health