Nemaline myopathy is a hereditary muscle disease that occurs secondary to mutations in at least 10 genes. It is usually evident at birth based on generalized muscle weakness and respiratory difficulites.
During pregnancy mothers often note the accumulation of excessive amniotic fluid and weak or absence of fetal movements in nemaline myopathy 10. Respiratory difficulties, joint contractures, feeding problems and generally weak muscles (hypotonia) are usually present at birth. Eye movements are minimal (ophthalmoplegia). The heart muscle seems to function normally. All patients have generalized muscle weakness.
This condition results from mutations in both copies of a gene that is important for normal muscle development. Carrier parents with a single mutation are clinically normal but there is a 25% chance that, if both carry the mutation, each child can inherit both mutant copies.
Respiratory failure often leads to death in the neonatal or early childhood period. However, one child has lived to 10 years of age and another to 4 years; both were dependent upon percutaneous gastrostomy tubes for nutrition. Breathing assistance is nearly always required. Walking often requires assistance. Physical therapy and special education can be of benefit in addition to supportive therapy.