Pneumococcal pyomyositis. Case report, review of the literature, and comparison with classic pyomyositis caused by other bacteria.

Pyomyositis is caused by staphylococci in 70% to 90% of patients. We report a case of pneumococcal pyomyositis (PP), review the 11 cases previously published, and compare the features of pneumococcal pyomyositis with those of classic (nonpneumococcal) pyomyositis. Several clinical characteristics have been identified that are notably different in both groups. Psoas muscle involvement was observed in two thirds of the patients with PP, and a source for the infection was identified in half of the patients. Patients with PP were older than those with classic pyomyositis. Men were affected less often than women with PP, but the opposite was the rule in classic pyomyositis. The systemic response to the infection was more prominent in patients infected with pneumococci than from other causes. Most patients with PP were successfully treated with antibiotics and drainage. Secondary meningitis was observed in 3 patients with psoas muscle abscess caused by pneumococci. Mortality is low in pyomyositis regardless of the causative pathogen.