CASE-OF-THE-MONTH - DECEMBER 1997 - A 48-YEAR-OLD WOMAN WITH CHRONIC MYALGIAS AFTER EXERCISE

A 48-year-old woman presented with long-standing exercise-induced weak ness and myalgias and more recent onset proximal weakness. The creatin e kinase was elevated and an electromyogram revealed abnormal spontane ous activity primarily in paraspinal muscles and scattered short durat ion motor unit potentials in some proximal limb muscles. A previous de ltoid muscle biopsy specimen revealed mild non-specific changes sugges tive of myopathy. A paraspinal muscle biopsy specimen revealed a vacuo lar myopathy with glycogen storage and absent phosphorylase staining. Biochemical studies confirmed phosphorylase deficiency. This case illu strates the importance of paraspinal investigation in patients with my opathy and shows that there may be histopathologic variability from mu scle to muscle in phosphorylase deficiency (McArdle's Disease).