Introduction: Pyomyositis, originally reported in tropical areas is a rare condition, most often caused by Staphylococcus aureus. Usually affecting large muscles of the body, it occurs more frequently in immunocompromised patients and is also related to risk factors such as intensive exercise, muscle trauma, malnutrition, bacteremia, chronic illnesses and concurrent infection. If misdiagnosed and not treated rapidly it can progress to toxic shock syndrome that is associated with high mortality rates.

Case Presentation: We were presented with an atypical case of pyomyositis of the forearm in a four-year-old male with the history of elbow trauma, concurrent infection and hypoproteinemia. When admitted to the hospital, the patient was febrile, with local symptoms of inflammation and increased parameters of inflammation. Magnetic resonance imaging (MRI) showed the presence of pyogenic infection of the brachial, pronator teres and flexor carpi radialis muscle. Pus drainage and lavage as well as intravenous administrating of double antibiotic therapy were performed. The patient was discharged ten days after being admitted to the hospital, with no complications.

Conclusion: Although pyomyositis is a rare condition usually affecting large muscles of the body, other muscles, such as forearm muscles, can also be atypically affected. Muscle trauma, concurrent infection and hypoproteinemia are reported to be risk factors for the disease that is most often caused by community-acquired methicillin-resistant Staphylococcus aureus. Rapid diagnosis and prompt treatment avoid progression to toxic shock syndrome associated with high mortality rates.

Keywords: Children; Elbow Joint; Forearm; Pyomyositis, Trauma