Muscle involvement in polyarteritis nodosa: report of a patient presenting clinically as polymyositis and review of the literature.

Muscle symptoms, especially myalgias, appear to be common in patients with polyarteritis nodosa (PAN). We describe a patient who presented with a generalized myopathy and elevated creatine kinase (CK) suggestive of polymyositis. However, subsequent exploratory surgery for an acute abdomen revealed colonic perforation on the basis of PAN. A review of the literature suggests that generalized myopathy and elevated CK are uncommon features of PAN. A muscle biopsy can be a helpful procedure to secure the diagnosis in patients with PAN especially those with myopathies. Strategies for optimizing the choice of biopsy site are discussed.