A 40 year old male with longstanding psoriatic arthritis on adalimumab for management of skin and joint disease develops increasingly severe mid-back pain. The pain started after lifting a heavy box at work. He describes the pain as constant, unrelieved by positional change and worse with activity. He has tried ibuprofen 800mg three times daily without symptomatic relief. The pain has been increasing in severity. His psoriatic arthritis and skin disease have been in excellent control for the past six years on therapy. He denies any fevers but describes malaise for the past week and mild anorexia. He has no radicular symptoms.

• Past Medical History: Hypertension, mild asthma
• Family and Social History: Brother with psoriasis and sister with Crohn’s disease; works full time in a factory’s shipping and receiving department. Non-smoker. Rare alcohol use on the weekend.
• Medications: Adalimumab 40mg sc every 14 days; hydrochlorothiazide 25mg daily; albuterol inhaler as needed; topical steroids as needed.
• Review of Systems: Weight loss of 4 lbs; no rash; minimal shortness of breath; no chest pain; no diarrhea or constipation; recent mild abrasion of elbow at work.
• General Physical Exam: Temperature 99.7; pulse 100; normal respirations; blood pressure 100/60. Skin exam shows left olecranon abrasion with surrounding erythema. Heart with tachycardia but no murmurs. Lungs clear. Abdomen is normal without rebound or tenderness. Neurologic exam is normal.
• Musculoskeletal exam: Prominent DIP enlargement; synovial thickening at left 3rd MCP; other peripheral joints are normal without tenderness. Percussion tenderness at T12 level.

What is your differential diagnosis?

Although psoriatic arthritis is one of the spondyloarthropathies that can have associated involvement in the axial spine, it is important to consider the entire history. The patient’s joint disease has been in very good control with adalimumab and it would be unusual to develop new inflammatory back pain on adequate therapy. The sudden onset of pain after lifting a box is concerning for possible mechanical injury or compression fracture. The latter would be unusual in this 40 year old male. However, he also has more generalized symptoms of fever, malaise and has low grade fever on ibuprofen. Given his immunosuppression with adalimumab and evidence of skin breakdown at his elbow, workup for possible infectious cause is strongly indicated.

How would you proceed in evaluating this patient?

General evaluation includes CBC with differential, electrolytes, creatinine, ESR, CRP, blood and urine cultures. If there is swelling of the olecranon bursa, an aspirate and culture can provide possible identification of organism.  Radiographs of area of point tenderness is the first imaging test but it is likely further imaging with MRI or CT scan is needed to exclude vertebral osteomyelitis, discitis or paravertebral abscess. Cardiac echo should be ordered to exclude endocarditis.