Angioedema is a swelling similar to hives, but the swelling is beneath the skin rather than on the surface. The swellings are called welts.Wikipedia
Hereditary angioedema types I and II are caused by a diverse group of mutations in the C1 inhibitor C1NH gene, while another type of hereditary angioedema, HAE type III, is caused by mutations in the coagulation factor XII F12 gene. In general, the different mutations give rise to angioedemas that are indistinguishable from each other.
Note that only a minority of the mutations reported to give rise to herediatary angioedema are currently represented in SNPedia; those that are include: