Apart from the common form, mediated by allergy, it has been reported as a side effect of some medications, in particular ACE inhibitors. Additionally, there are three autosomal dominant inherited forms known, due to mutations in the genes that control the clotting cascade, including the SERPING1 gene, which results in deficiency of the blood protein C1-inhibitor (type I HAE) and the F12 gene, which controls Factor XII (type III HAE). There is an additional type in which C1 levels are normal but C1 function is decreased (type II HAE). All three forms are called hereditary angioedema (HAE) or occasionally by the outdated term 'hereditary angioneurotic edema' (HANE). In all forms of HAE, swelling may also occur in the digestive tract and other organs. It is life-threatening when it involves the larynx due to the potential for asphyxiation.