Streptococcus agalactiae myositis in a child with perinatally acquired human immnodeficiency virus.

Pyomyositis is a musculoskeletal infection with formation of an intramuscular abscess. Endemic in tropical climates, it is being reported with increasing frequency in temperate climates such as the United States. The most common causative organism is Staphylococcus aureus, present in greater than 90% of reported cases. Risk factors include underlying chronic illness, malnutrition, immunocompromised state, and muscle trauma. We present a case in which Streptococcus agalactae was the causative agent of myositis in a child with a history of perinatally derived human immunodeficiency virus infection.