Pyomyositis

A case of Pyomyositis by Sarah Kerr

1. Noon Conference Sarah Kerr, MS3

2. Summary Statement Patient is a 59-year-old man with ALL who presented for cycle 2B of hyper-CVAD chemotherapy but on further evaluation was found to have leukocytosis, as well as worsening R elbow and R thigh erythema, edema and pain. DDx?

3. Imaging MRI Upper Extremity: Myositis; no evidence of abscess, osteomyelitis or septic arthritis. MRI Lower Extremity: Focal intramuscular abscess in the biceps femoris muscle with mild necrosis of the surrounding tissue.

4. Pyomyositis A purulent infection of skeletal muscle that arises from hematogenous spread of bacteria – usually with abscess formation. Predisposing factors: immunodeficiency, trauma, injection drug use, concurrent infection.

5. Pyomyositis Most common pathogen = staph aureus (MRSA in up to 25% of these cases). E. Coli pyomyositis emerging infection in those with hematologic malignancy.

6. Clinical Presentation FEVER, LOCALIZED CRAMPY MUSCLE PAIN, SWELLING 3 clinical stages Greater than 90% of patients present with stage 2: occurs 10-21 days after onset of symptoms and can be characterized by fever, exquisite muscle tenderness, edema, marked leukocytosis. Frank abscess MAY be clinically apparent. Aspiration yields pus.

7. Diagnosis MRI Fluid cultures

8. Treatment Patients who present with stage 2 or 3 usually require drainage in addition to antibiotic therapy. Immunocompetent: vancomycin. Immunocompromised: vancomycin + broad-spectrum coverage for gram neg. and anaerobes.

9. Pyomyositis Polymyositis Pathophysiology Hematogenous spread of bacteria in immunocompromised patient Autoimmune Clinical Presentation Fever, swelling, crampy localized muscle pain Symmetric proximal muscle weakness Diagnostics MRI, Fluid aspirate Muscle enzymes, +ANA/anti-jo-1, muscle biopsy Treatment Broad-spectrum antibiotics Corticosteroids, methotrexate