A Head-Scratcher: Humira Causing Enthesitis of the Skull in a Patient with Crohnʼs?

Abstract

Enthesopathy of the skull has been described in association with ankylosing spondylitis, psoriatic arthritis and reactive arthritis. Enthesitis, inflammation of the bone insertion sites of tendons and ligaments, typically occurs in the heels and knees of individuals with inflammatory bowel disease. This is the first report of an individual with Crohn's disease managed with adalimumab who presents with skull enthesitis without spondyloarthropathy or psoriatic arthritis. A 40 year old woman with a history of Crohn's disease involving her stomach, small bowel and colon without extraintestinal manifestations presented following an emergency room evaluation for posterior skull pain. Her disease had been previously managed with 6-mercaptopurine (discontinued due to hepatotoxicity) and infliximab (discontinued due to serum sickness). She was being treated with adalimumab 40 mg weekly for 15 months with clinical and histologic remission of her gastrointestinal disease. In the emergency room, she described 2 days of progressively worsening posterior skull pain. Examination revealed 5 areas of localized, posterior skull tenderness. Her labs were unremarkable, including inflammatory markers (ESR 2, CRP 0.1). She was diagnosed with skull enthesitis and treated with prednisone with improvement but without complete resolution. Subsequent allergy consultation was notable for persistent posterior skull tenderness and cervical adenopathy. Rheumatology evaluation confirmed enthesitis. Her skull pain gradually resolved with a 3 week course of tapering prednisone. She was advised by the allergist to discontinue adalimumab. This is an unusual case of skull enthesitis in an individual with inflammatory bowel disease without extraintestinal symptoms who was maintained on adalimumab. While adalimumab has been associated with adenopathy, it has not been reported to result in enthesitis. It is uncertain if this patient has IBD-associated enthesitis or medication-induced side effects. Continued observation for similar circumstances can provide clarification of the etiology of enthesitis in individuals with inflammatory bowel disease and offer potential guidance for management.