A disorder in which a vascular tumour of the adrenal medulla (see ADRENAL GLANDS) develops. The tumour may also affect the structurally similar tissues associated with the chain of sympathetic nerves. There is uncontrolled and irregular secretion of ADRENALINE and NORADRENALINE with the result that the patient suffers from episodes of high blood pressure (HYPERTENSION), raised heart rate, and headache. Surgery to remove the tumour may be possible; if not, drug treatment may help.