In patients with Crohn's disease arthritis of the large joints, osteomalacia, osteoporosis and aseptic bone necrosis as a consequence of malabsorption and glucocorticoid intake may occur. The case of a patient with long-standing Crohn's disease is presented who subsequently developed abacterial osteomyelitis of the jaw ("osteomyelitis sicca"). The symptoms of the osteomyelitis improved under immuno-suppressive therapy. Because the etiopathogenetic concepts for Crohn's disease and osteomyelitis sicca are similar, the latter could be a rare extraintestinal manifestation in Crohn's disease, not described previously.