The vast majority of people with HAE have a defect in the gene that controls a blood protein called C1-Inhibitor. This defect causes a biochemical imbalance that produces swelling. HAE is also known as C1-Inhibitor Deficiency – Type I and Type II. People diagnosed as having HAE with Normal C1-Inhibitor experience swelling symptoms generally similar as seen in Type I and II. Globally, scientists are researching how to better understand the underlying genetic and biochemical causes and find treatments for the very important members of our community who suffer from HAE with Normal C1-Inhibitor.
HAE is hereditary and children have a 50% chance of inheriting HAE if one of their parents has the condition. However, the absence of a family history does not rule out the diagnosis of HAE, as scientific reports indicate that as many as 25% of HAE cases result from a spontaneous mutation of the C1-Inhibitor gene at conception. Children of people with HAE may also inherit the condition.