<cardiology, dermatology, embryology, physiology> A haemangioma or arteriovenous malformation is a tangle of abnormal vessels that forms an abnormal communication between the arterial and venous systems.

Most are congenital and result from improperly formed angioblastic tissue in the foetus. If large enough, they may produce a shunt of sufficient magnitude to raise the cardiac output. Arteriovenous malformations may occur in the brain, brainstem and spinal cord, where they may cause headaches, seizures or bleeding (subarachnoid haemorrhage).

Red or purple-coloured vascular skin markings that develop shortly after birth. most are usually painless and benign. Some lesions (cavernous haemangiomas) will disappear or become harder to see as the child approaches school age. Localised steroid injections have been used successfully to reduce the size of a birthmark.

American spelling: hemangioma

(11 Feb 2009)