Mondo Description Late-onset distal myopathy, Markesbery-Griggs type is a rare, genetic, non-dystrophic myofibrillar myopathy disorder characterized by late-adult onset of distal and/or proximal limb muscle weakness with initial involvement of posterior lower leg muscles, medial gastrocnemius and soleus. Patients present with ankle weakness followed by weakness of finger and wrist extensors and later on of proximal muscles. Ambulation is usually preserved. Late-onset associated cardiomyopathy and/or neuropathy has been reported in a minority of cases.

Uniprot Description A form of myofibrillar myopathy, a group of chronic neuromuscular disorders characterized at ultrastructural level by disintegration of the sarcomeric Z disk and myofibrils, and replacement of the normal myofibrillar markings by small dense granules, or larger hyaline masses, or amorphous material. MFM4 is characterized by distal and proximal muscle weakness with signs of cardiomyopathy and neuropathy.