A 75-year-old woman with systemic lupus erythematosus was evaluated for two months of chronic, low back pain. She also reported subjective fevers, weight loss, and an initially necrotic, one-centimeter wound on her right calf that developed five months earlier. She had no history of trauma, paraspinal steroid injections, or past cardiac or spine surgery. Medications are significant for prednisone and hydroxychloroquine.
On exam she was afebrile, with normal vitals, mild lumbar tenderness, normal strength, and intact reflexes in the lower extremities and without saddle anesthesia.
Laboratory analysis showed normocytic anemia (hemoglobin 11.6 g/dL), normal white blood cells (5.4 x 109/L), normal platelets (175 x 109/L), hyponatremia (124 mmol/L), and elevated erythrocyte sedimentation rate (106 mm/hr) and C-reactive protein (117 mg/L). She had normal serum complement levels, a negative HIV, and an indeterminate QuantiFERON test.
MRI with and without contrast of the thoracic and lumbar spine revealed multilevel discitis and prevertebral osteomyelitis at L1-2, L2-3, and L5-S1 (Figure 1). An abscess located in L5-S1 (Figure 1(a), white arrow) was aspirated. Culture of the abscess revealed polymorphonuclear cells without organisms on conventional and acid-fast bacilli staining. Bacterial and fungal microscopy of the abscess and blood cultures were obtained. Cryptococcal PCR, Coccidioides antibody, and Mycobacterium tuberculosis polymerase chain reaction were negative.
The patient was started on empiric intravenous vancomycin and ertapenem. On day 12, M. chimaera was identified in the abscess aspirate by culture and sequencing. She was then transitioned to clarithromycin, rifampin, and ethambutol. A new biopsy of the calf wound was positive for M. chimaera. Surgical discectomy, debridement, and fusion were recommended; however, she deferred surgery and was discharged with a prolonged course of antimycobacterials.