Hereditary angioedema is an inherited disorder. It is caused by low levels or improper function of a protein called C1 inhibitor. This, in turn, affects blood vessels. People with hereditary angioedema can develop rapid swelling of the hands, feet, limbs, face, intestinal tract, or airway (larynx or trachea). Unlike an allergic reaction, there is usually no itching or hives. Swelling of the gut can cause intestinal cramping. If swelling closes the airway, it can be fatal. Attacks of swelling can become more severe in late childhood and adolescence. There is usually a family history of the condition, but this may only reported to descendants as an unexpected, sudden, and premature death of a parent, aunt, uncle, or grandparent.
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