Nemaline myopathy is usually genetic and shows traits in the affected individual from birth or an early age. However, there are some cases of symptoms of nemaline myopathy not showing up until adulthood. These cases are usually not genetic. Of the genes that have been linked to nemaline myopathy, most are also involved in encoding proteins in the sarcomeres in the muscle cells. Respiratory muscles are often more affected than other skeletal muscle groups. Cardiac muscle is usually not affected in nemaline myopathy; however, in cases where it does, patients often present with dilated cardiomyopathy. The ocular muscles are usually spared.