Hereditary angioedema (HAE) is caused by low levels or improper function of a protein called C1 inhibitor. This problem affects the blood vessels. People with hereditary angioedema can develop rapid swelling of the hands, feet, limbs, face, intestinal tract, larynx (voicebox), or trachea (windpipe).
Attacks of swelling can become more severe in late childhood and adolescence.
There is usually a family history of the condition. However, relatives may be unaware of previous cases, which may have been reported as an unexpected, sudden, and premature death of a parent, aunt, uncle, or grandparent.
Dental procedures, sickness (including colds and the flu), and surgery may trigger attacks of hereditary angioedema.