What is nemaline myopathy?
Nemaline myopathy (NM) is a group of inherited disorders that affects muscle tone and strength. At various stages in life, the shoulder, upper arm, pelvic and thigh muscles may be affected. Symptoms usually begin between birth and early childhood. There are two main forms of NM:
- Typical – is the most common form, usually presenting in infants with muscle weakness and floppiness. It may be slowly progressive or non-progressive, and most adults are able to walk.
- Severe – is characterized by absence of spontaneous movement or respiration at birth, and is often fatal in the first few months of life. Occasionally, late-childhood or adult-onset can occur.
NM is considered rare, affecting approximately 1 in 50,000 people. NM can be caused by a mutation in one of several different genes responsible for making muscle protein.
Symptoms vary depending on the age of onset and the type of NM. They may include:
- poor muscle tone and weakness (especially in the face, neck, upper arms and legs)
- delay or inability to walk
- breathing problems
- difficulty feeding and swallowing
- speech difficulties
Journal of Child Neurology, 2012