Coarctation occurs in ~7% of patients with congenital hea disease, is more common in males than females, and is paicularly frequent in patients with gonadal dysgenesis (e.g., Turner syndrome). Clinical manifestations depend on the site and extent of obstruction and the presence of associated cardiac anomalies; most commonly a bicuspid aoic valve. Circle of Willis aneurysms may occur in up to 10%, and pose a high risk of sudden rupture and death. ( Harrison&;s principle of internal medicine,18th edition,pg no. 1925)