Distal myopathy with focal granular degenerative change in vacuolated type 2 fibers.

A slowly progressive distal myopathy with raised blood (CK) level commencing in the second decade was associated with large vacuoles found only in type 2 fibers. The vacuoles consisted of sarcoplasmic spaces without limiting membranes, containing granular and fibrillar material. This material probably represented degenerative products derived from myofibrils. A distinction is drawn between these degenerative vacuolar changes and those reported in other cases of sporadic or hereditary distal myopathy in which autophagic vacuoles are characteristic.