Nemaline myopathy (NM) is a group of congenital, hereditary neuromuscular disorders that cause muscle weakness, generally nonprogressive, of varying severity where severe forms show up to 66% mortality rates before the age of two. It is considered one of the most severe muscle conditions of childhood. Currently no treatments or disease modifying therapies exist for nemaline myopathy and few potential candidate drugs have been identified.

“Myopathy” means “muscle disease”, and a biopsy of muscle from a person with nemaline myopathy shows abnormal thread–like rods, called nemaline bodies, in the muscle cells. People with nemaline myopathy (or NM) usually experience delayed motor development and weakness in the arm, leg, trunk, throat, and face muscles.

The disorder is often clinically categorized into several groups, including mild (typical), intermediate, severe, and adult–onset; however, these distinctions are somewhat ambiguous, as the categories frequently overlap. Respiratory problems are a primary concern for people with all forms of NM, and though in some severe cases they may threaten life expectancy, aggressive and proactive care allows most individuals to survive and lead active lives.