Next Topic Inheritance of Hereditary Angioedema

Hereditary angioedema (HAE) affects between 1 in 10,000 to 1 in 50,000 people. The majority of people with HAE inherit a C1 esterase inhibitor (C1-INH) defect from one of their parents. A parent with HAE has a 50% chance of passing the condition on to a child of either sex.

In Figure 1, below, the father has HAE and has a change on one of his C1-INH genes. Each of his children, regardless of sex, has a 50% chance to inherit the defective C1-INH gene from him. HAE is defined as a “dominant” condition because it only takes a change in one of the two C1-INH genes a person carries to cause the disease.

In some patients, HAE is not inherited and results from a new spontaneous change in the sperm or egg cell that created his/her specific pregnancy. In one analysis of patients without a family history of HAE, but with low levels of C1-INH and recurrent angioedema, 25% of newly diagnosed patients with HAE had C1-INH changes that were new rather than inherited.

Figure 1: Inheritance Pattern of HAE: Autosomal Dominant

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