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

Abstract

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.

Keywords: fatty liver disease; methicillin-sensitive bacteremia; pyomyositis; sacroiliac joint septic arthritis; staphylococcus aureus.

Figure 1. Lumbar spine MRI showing enhancement of the posterior paraspinal muscles on the left side at the L4-L5 level. No osseous enhancement or abscess was present.

Figure 2. Lumbar spine MRI showing questionable associated epidural enhancement at the L5-S1 level, likely infectious in nature. No abscess or drainable collection was noted.

Figure 3. MRI of the pelvis with and without contrast showing the 5.5 x 1.2 x 5.7 cm presacral abscess formation.

Of note, there was an intradural extension at the level of the left S1 and S2 neural foramen. Phlegmonous change over the lateral aspect of the left gluteus maximus muscle belly deep to the iliotibial band with small-volume abscess formation. No evidence of acute osteomyelitis.

Figure 4. Irregular edema and enhancement in the left gluteus maximus, piriformis, iliacus, posterior psoas, and left paraspinal muscles, indicative of pyomyositis.