Myofibrillar myopathies (MFM)
are a group of neuromuscular disorders characterized by slowly progressive weakness that can involve both proximal muscles (such as hips and shoulders) and distal muscles (those farther away from the trunk). Some affected individuals also experience sensory symptoms, muscle stiffness, aching, or cramps. Peripheral neuropathy or cardiomyopathy may also be present. Most people with MFM begin to develop muscle weakness in mid-adulthood, but features of the condition can appear anytime between infancy and late adulthood. It may be caused by mutations in any of several genes, including DES, CRYAB, MYOT, LDB3, FLNC, and BAG3; the signs and symptoms of MFM can vary widely depending on the condition's genetic cause. It is inherited in an autosomal dominant manner. Treatment may include a pacemaker and implantable cardioverter defibrillator (ICD) for arrhythmia or cardiac conduction defects; cardiac transplantation for progressive or life-threatening cardiomyopathy; respiratory support for respiratory failure; and physical therapy and assistive devices for those with advanced muscle weakness. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.