What cause hereditary angioedema?

HAE: Hereditary angioedema (hae) is caused by a an uncontrolled activation of a complex cascade of proteins called complement. Hae is a result of a deficiency or lack of functional c1 esterase inhibitor protein. Some patients are born with this problem while other may acquire a lack of c1 esterase inhibitor from an underlying disease such as cancer. There are new treatments available.