Achilles tendinitis as a rare extraintestinal manifestation of ulcerative colitis

Patients with inflammatory bowel disease often have extraintestinal manifestations (EIMs) involving almost all organ systems, but little has been reported on Achilles tendinitis. Herein, we present a unique case of Achilles tendinitis, which manifested shortly after initiation of mesalazine therapy for ulcerative colitis. A 26-year-old Japanese woman with bloody diarrhea and abdominal cramps lasting for 7 days was referred to our hospital. The Lichtiger clinical activity index (CAI) score was 9 at the first visit. Based on the clinical symptoms and examination results, she was diagnosed with ulcerative pancolitis in the active phase, and treatment with mesalazine (2.4 g/day) and probiotics was initiated. Her symptoms resolved within 7 days of treatment (CAI 3). However, she then developed bilateral Achilles tendinitis without any apparent cause. The Achilles tendinitis subsided with conservative management within 2 weeks, despite continuation of mesalazine therapy. This case instructively suggests that Achilles tendinitis should be noted as an EIM of ulcerative colitis.