Epidemic influenza myopathy in Cincinnati in 1977.

A distinctive myopathy was observed in 24 children following influenza B infection. The abrupt onset of severe muscle pain and difficulty in walking began as the respiratory symptoms were waning. The lower extremities, particularly the gastrocnemius and soleus muscles, were involved preferentially. Nasopharyngeal cultures were positive for influenza B Hong Kong in 18 of these patients. Serum creatine phosphokinase levels were significantly elevated (mean 55.2 units) when compared to controls and nine patients with Reye syndrome. The cardiac muscle isoenzyme was detected in the serum of 17 myopathy patients. Serum glutamic oxaloacetic transaminase, but not serum glutamic pyruvic transaminase, was elevated compared to controls (P less than 0.01) but less (P less than 0.001) than the patients with Reye syndrome. Twelve patients underwent muscle biopsy; segmental rhabdomyolysis without inflammation was detected in nine patients. Myopathy is a complication of influenza infection that can be diagnosed by clinical, biochemical, and virologic examination.