Myofibrilar myopathy (MFM) is a neuromuscular disease characterized by slowly progressive muscle weakness that can involve both proximal muscles (such as hips and shoulders) and distal muscles (those further away from the trunk). Some affected individuals also experience muscle stiffness, aching, or cramps. Other symptoms that can be associated with MFM include pain and tingling in the limbs (peripheral neuropathy) or an enlarged and weakened heart (cardiomyopathy). Most people with MFM begin to develop muscle weakness in mid-adulthood, but features of the disease can appear anytime between infancy and late adulthood.
MFM is caused by a mutation (change) in any of several genes, including DES, CRYAB, MYOT, LDB3, FLNC, BAG3, FHL1, TTN, and DNAJB6. The signs and symptoms of MFM can vary depending on the genetic cause. For some people, the exact genetic cause may be unknown.
The mode of inheritance of the disease depends on exactly which gene is changed.
Treatment may include physical therapy and assistive devices such as a cane or wheelchair for those with advanced muscle weakness. Affected individuals who have cardiomyopathy or an abnormal heart rhythm (arrhythmia) may require a pacemaker or implantable cardioverter defibrillator (ICD).
Myofibrillar myopathy (MFM) primarily affects skeletal muscles, which are muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected. The signs and symptoms of MFM vary among affected individuals, typically depending on the exact genetic cause of the disease. Most people with this disease begin to develop muscle weakness (myopathy) in mid-adulthood. However, features of this disease can appear anytime between infancy and late adulthood.
Muscle weakness most often begins in the hands and feet (distal muscles), but some people first experience weakness in the muscles near the center of the body (proximal muscles). Facial muscle weakness can rarely cause swallowing and speech difficulties. The muscle weakness is progressive, meaning that it tends to worsen over time.
Other signs and symptoms of MFM can include an enlarged and weakened heart muscle (cardiomyopathy) or an abnormal heart rhythm (arrhythmia), muscle pain (myalgia), and loss of sensation and weakness in the limbs (peripheral neuropathy). For some people, as the disease progresses, the muscles of the lungs may also be affected, which can result in respiratory failure. Individuals with this disease may have skeletal problems including joint stiffness (contractures) and abnormal curvature of the spine (scoliosis). Rarely, people with this disease develop clouding of the front surface of the eyes (cataracts).
This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the
5%-29% of people have these symptoms
- Right ventricular cardiomyopathy
1%-4% of people have these symptoms
- Bradycardia Slow heartbeats
- Dilated cardiomyopathy
- Stretched and thinned heart muscle
- Hypertrophic cardiomyopathy
- Enlarged and thickened heart muscle
- Restrictive cardiomyopathy
NIH genetic and rare disease info
Myopathy is a rare disease.