ImmunoDeficiency Resource (IDR)

Defects in F12 are the cause of factor 12 deficiency (F12 deficiency) [mim:234000]; also known as Hageman factor deficiency. This trait is an asymptomatic anomaly of in vitro blood coagulation. Its diagnosis is based on finding a low plasma activity of the factor in coagulating assays. It is usually only accidentally discovered through pre-operative blood tests. F12 deficiency is divided into two categories, a cross-reacting material (crm)-negative group (negative f12 antigen detection) and a crm-positive group (positive f12 antigen detection). Hereditary angioedema is episodic and asymptomatic in most patients. There are 3 types of the disorder. In type I, representing 85% of patients, serum levels of C1NH are less than 35%. In type II, the levels are normal or elevated, but the protein is nonfunctional. The two types are clinically similar. In HAE type III patients have normal C1-inhibitor concentration and function and a missense mutation in F12. Patients are exclusively women and their episodes of angioedema are precipitated or worsened by high estrogen levels.