Methicillin-Sensitive Staphylococcus aureus Bacteremia, Septic Arthritis, and Pyomyositis in a Young Male: A Case Report and Review of the Literature.

We share a case of a 38-year-old male with a history of hypertension and metabolic dysfunction-associated steatotic liver disease (MASLD) who was admitted for septic arthritis of the left sacroiliac joint, pyomyositis, and associated methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia. The patient presented with left hip pain, fever, tachycardia, and leukocytosis. A physical exam revealed left lateral hip tenderness and limited range of motion. Lumbar spine magnetic resonance imaging (MRI) revealed left sacroiliac septic arthritis, inflammation of multiple muscles consistent with pyomyositis, and a presacral abscess. Blood cultures and ​polymerase chain reaction results confirmed MSSA bacteremia, though no common predisposing risk factors were identified. The abscess was aspirated and the patient was treated with oxacillin and cefazolin. He showed clinical improvement with stable leukocytosis and was discharged on cefazolin via a peripherally inserted central catheter. Follow-up included a referral to rheumatology and a repeat of lumbar spine MRI. This case underscores the challenges in diagnosing MSSA bacteremia, especially in the absence of typical risk factors, and emphasizes the critical role of clinical suspicion and appropriate treatment strategies.