|Although infantile-onset nemaline myopathy tends to be the most severe type, these children can survive to adulthood.|
Nemaline myopathy is an inherited myopathy, a group of diseases that causes problems with the tone and contraction of skeletal muscles. It gets its name from the fact that the muscle cells contain abnormal clumps of threadlike material — probably disorganized filament proteins — called nemaline bodies (nema is Greek for “thread”).
It also is called rod body disease because the clumps can look either thready or more rodlike with different stains and under different levels of magnification.
Nemaline myopathy causes weakness and poor tone (hypotonia) in the muscles of the face, neck and upper limbs, and often affects the respiratory muscles (those that control breathing).
The infantile-onset cases tend to be the most severe. Usually, infants with the disease lack the muscle strength and tone required for simple postures and movements. They also have serious difficulties with feeding and respiration.
For adults, even noncongenital forms of the disease can cause life-threatening respiratory problems. Adults also might experience swallowing and speech problems, and those with restricted mobility might develop scoliosis. See Signs and Symptoms.
This disease is caused by a variety of genetic defects, each one affecting one of the filament proteins required for muscle tone and contraction. It can be inherited in an autosomal recessive or autosomal dominant pattern, meaning it can be produced by defective genes contributed by either one or both parents. See Causes/Inheritance.
Onset occurs from birth to adulthood. While respiratory failure or lung infections can be life-threatening in infancy, some affected infants survive to adulthood.
Affected children usually attain motor milestones slowly, and at puberty they might experience further weakening. However, even people who have had the disease since birth can lead active lives.
In the 1990s, MDA-supported researchers discovered that defective filament proteins give rise to nemaline myopathy. They continue to work to understand the molecular basis of this disease and to investigate potential treatments. See Research.