Bloody diarrhoea: a rare presentation of a systemic disease.

Bloody diarrhoea in adolescents is usually due to enteric infection or inflammatory bowel disease. We describe a patient with bloody diarrhoea and endoscopic features of colitis in association with a systemic vasculitis. Positive anti-proteinase-3 antineutrophil cytoplasmic antibodies and cutaneous vasculitis on biopsy confirmed the diagnosis of Wegener's granulomatosis. He was started on high dose steroids and cyclophosphamide but required plasmapheresis for a declining renal function. The case highlights the need for vigilance with common clinical problems, because a life-threatening condition may be averted by prompt recognition and urgent therapy with immunosuppressants.