Infectious myositis. A tropical disease steals out of its zone.

Infectious myositis is an acute infection of skeletal muscle that is increasing in prevalence with the increased incidence of HIV disease. Typical presentation is asymmetric swelling of an isolated muscle, with exquisite pain and fever. Results of laboratory studies are usually nonspecific, but magnetic resonance imaging of the affected area suggests the diagnosis. Muscle biopsy and direct identification of the pathogen on tissue culture are required, because the list of potential pathogens is long. With prompt treatment, most patients achieve complete resolution and return to their preinfection level of health.