Isolated progressive muscle weakness with tubular aggregates.

We report 2 isolated cases of slowly progressive muscle weakness in which tubular aggregates in muscle biopsy were found as the major pathological feature. Tubular aggregates were present in both types of fibers. Electron microscopy revealed the accumulation of double-walled tubular structures in dense subsarcolemmal locations or in smaller amounts within the myofibrils, close to cytoplasmic organelles. Myopathy with tubular aggregates is believed to form a distinct clinico-pathological entity with 3 well-distinguished clinical groups. The cases reported herein would fall into the group of sporadic isolated progressive muscle weakness of which only 3 other cases have been previously described.