A Case of Progressive Quadriceps Weakness and Elevated Creatine Kinase Level Mimicking Inclusion Body Myositis

摘要

The patient initially sought medical attention in 2001 at age 58 years. His presenting symptoms had started ~2 years previously and included difficulty getting up from a seated position. This slowly progressed to involve severe weakness and atrophy of the quadriceps muscles (left side greater than the right side) (Figure 1). The patient's initial evaluation included an elevated creatine kinase (CK) level (>l,500 units/liter). A muscle biopsy sample of the right quadriceps was performed, which demonstrated marked variation in fiber size, numerous degenerating and regenerating muscle fibers, and scattered foci of primary lym-phocytic infiltration (Figure 2). No perivascular inflammatory infiltrates or rimmed vacuoles were observed. A trial of prednisone (for presumed polymyositis) produced only a modest and temporary reduction in CK level, but his weakness did not improve. Subsequent trials of azathio-prine and methotrexate also failed to produce any symptomatic improvement. Two additional muscle biopsies were performed, both in the left quadriceps. The first, performed in 2003, showed similar findings to the initial sample. Additional immunohistochemical staining for dystrophin, dysferlin, sarcoglycans, and merosin was normal. The next biopsy, performed in 2004, contained only fibroadipose tissue. Immunostaining against class I major