Factor XII deficiency (2 variants)

Factor XII deficiency, also known as Hageman deficiency, is the most common congenital coagulopathy in domestic cats. Blood coagulation (clotting) is regulated by a complex cascade of plasma proteins, an essential process that prevents bleeding at the site of injury.

One of these key proteins is coagulation factor XII (also referred to as FXII, F12, or factor 12). Mutations in the F12 gene disrupt the normal function of FXII, leading to prolonged activated partial thromboplastin time (aPTT) and activated clotting time (ACT). Two known variants (147 and 533) are associated with reduced or complete loss of FXII activity, resulting in impaired blood coagulation. Variant 147 is more widespread, while variant 533 is less common but equally severe.

Both variants cause FXII deficiency, leading to an absence or significant reduction of detectable factor XII in feline plasma. Cats homozygous for either mutation have a severe deficiency and are at increased risk of excessive bleeding after surgery or even minor trauma. Heterozygous cats generally show a moderate reduction in FXII activity, although mild clinical signs have also been reported.

In the literature, an autosomal recessive inheritance pattern is suggested. However, mild clinical features in heterozygous cats have also been described. If both variant 147 and variant 533 are present in a heterozygous state, no functional FXII protein is produced, and the cat is considered homozygous affected.