Abnormal anastomosis of peripheral pulmonary arteries, initially suspected to be an arteriovenous fistula, in an adult with Williams syndrome.

Abnormal anastomosis of peripheral pulmonary arteries is rare and resembles a pulmonary arteriovenous fistula; thus, when the inflow or outflow route cannot be clearly identified in a suspected pulmonary arteriovenous fistula, the possibility of peripheral pulmonary artery anastomosis should be considered. However, the final diagnosis requires a catheterization study.