Back Pain and Immunosuppression: What's at the Root of it All?

Abstract

A32-year-old woman with systemic lupus erythematosus (SLE) on immunosuppressive medications presented to the Walter C Mackenzie Health Sciences Centre, Edmonton, Alberta, with a three-day history of right wrist swelling. She also complained of chronic midthoracic back pain in the setting of documented steroid-induced osteoporosis. Her back pain had increased over the six months before admission. She had also developed bilateral radicular pain, limited mobility, leg weakness, urinary hesitancy and a subjective change in light touch sensation of the legs. Bowel function was normal. She had night sweats but no fever or weight loss. There was no history of travel outside Alberta nor was there animal exposure. When well, the patient worked as a teacher’s aide. There was no personal or exposure history to suggest past tuberculosis (TB) infection. She was admitted for investigation, pain control and wrist aspiration. Past medical history was notable for Staphylococcus aureus joint infections, steroid-induced diabetes, shingles, remote pulmonary embolism, chronic recurrent skin and soft tissue infections, and a Salmonella dublin bacteremia 10 months before this admission. Medications at admission included prednisone, chloroquine, cyclophosphamide, metformin and hydromorphone. Physical examination revealed a pale, afebrile woman in moderate discomfort. Respiratory, cardiac and abdominal examinations were within normal limits. Musculoskeletal examination revealed an ‘exaggerated thoracic kyphosis’ at approximately T8. Joint examination was normal with the exception of decreased range of motion at the right wrist secondary to swelling, with minimal erythema and tenderness. Limb strength and reflexes were equal, with downgoing plantar responses. Admission laboratory data were as follows: hemoglobin 107 g/L, platelets 400×10/L, white blood cells 4.3×10/L with lymphocytes of 0.4×10/L. Serum urea and creatinine were normal. Serum transaminases, bilirubin and the international normalized ratio were within normal limits and the alkaline phosphatase was elevated at 157 IU. Complement levels were low and the sedimentation rate was 43 (mm/h). On admission and subsequently, the blood cultures were all negative. The right wrist aspirate revealed a small amount of noninflammatory fluid, which was negative on Gram stain and culture. A bone scan was performed, which revealed diffuse increased uptake in both wrists, consistent with an ‘arthritic process’, and there was ‘intensely increased’ uptake in the