Myofibrillar myopathies

Myofibrillar myopathies (MFM) represent a group of muscular dystrophies withsimilar morphologic but divergent clinical features. The pathologic hallmark of thedisease is disintegration of the Z-disks followed by myofibrillar degeneration,accumulation of filamentous myofibrillar degradation products, and of an array ofectopically expressed proteins and sometimes congophilic material. The clinical featuresof the MFM vary from slowly progressive distal weakness or weakness affecting musclesin a limb-girdle or a scapuloperoneal pattern. Cardiomyopathy and peripheral neuropathyare frequent associated features. EMG of the affected muscles reveals myopathic motorunit potentials accompanied by abnormal electrical irritability and neurogenic findings insome patients. To date, all MFM mutations have been traced to Z-disk-associatedproteins, namely, desmin, αB-crystallin, myotilin, ZASP, filamin C, Bag3, FHL1, andDNAJB6.