HAE is called hereditary because the genetic defect is passed on in families.
A child has a 50 percent possibility of inheriting this disease if one of the parents has it. The absence of family history does not rule out the HAE diagnosis, however.
Scientists report that as many as 20 percent of HAE cases result from patients who had a spontaneous mutation of the C1-Inhibitor gene at conception. Consequently, these patients can pass the defective gene to their offspring.
Because the disease is very rare, it is not uncommon for patients to remain undiagnosed for many years.
A large number of patients report that their frequent and severe abdominal pain was inappropriately diagnosed as psychosomatic, resulting in referral for psychiatric evaluation.
Unnecessary exploratory surgery has been performed on patients experiencing gastrointestinal edema, because abdominal HAE attacks mimic a surgical abdomen.
Before therapy became available, the mortality rate for airway obstruction was reportedly as high as 30 percent.