Acquired arteriovenous malformation induced by pressure: a case report.

Arteriovenous malformations may be congenital or acquired. In the latter case, usually a traumatic injury to the arteries precedes the arteriovenous anastomoses. Two elderly patients presented with large, purple-colored verrucous tumors on the buttocks. Both patients were obese and immobile, and reported repeated bleeding from the lesions after minor trauma. The tumors were soft and could be emptied by applying pressure. Doppler examination revealed arterial pulsations over the lesions. Both cases were diagnosed as pressure-induced arteriovenous malformations. The lesions are assumed to have been caused by tissue damage in the deep subcutis induced by decubitus.