Collagenous colitis and cutaneous polyarteritis nodosa in the same patient.

Collagenous colitis is associated with chronic diarrhoea and inflammatory changes detected by colonic biopsy, but no endoscopic abnormalities. Cutaneous polyarteritis nodosa shows the same histopathology as systemic polyarteritis nodosa, but is limited to the skin. Both diseases are rare and of unknown aetiology. Collagenous colitis has been described in association with different autoimmune disorders. We report on a case of collagenous colitis and cutaneous polyarteritis nodosa. To our knowledge, this association has not been reported previously.