The initial symptoms of Crohn's disease (CD) sometimes present as extraintestinal lesions, which can be a diagnostic challenge for physicians. Painful legs, known as "gastrocnemius myalgia syndrome", are rare complications that often precede abdominal manifestations. We herein report the case of a 38-year-old man who presented with bilateral leg myalgia lasting for 4 months. Magnetic resonance imaging showed abnormal intensity, and a muscle biopsy revealed inflammatory cell infiltration. Abdominal symptoms appeared three months after the myalgia onset, and the diagnosis of CD was confirmed later by endoscopic and radiological findings. To our knowledge, this is the first description of gastrocnemius myalgia syndrome in Japan.
Keywords: Crohn's disease; extraintestinal manifestation; gastrocnemius myalgia syndrome.