Factor XI deficiency is a hereditary haemostatic disorder. Factor XI participates in the intrinsic pathway of coagulation and its deficiency prolongs the activated partial thromboplastin time (aPTT), producing a mild to moderate bleeding diathesis. Affected cats bleed more than expected after surgeries, dental extractions or trauma, although severe spontaneous haemorrhages are uncommon.

It is associated with the Maine Coon (Kuder et al. 2022; OMIA:000363-9685); published carrier frequencies are limited. It is a probably underdiagnosed disease because its clinical expression is subtle and may go unnoticed without laboratory tests.

- Prolonged bleeding after surgery or wounds\n- Easy bruising\n- Persistent oral or dental haemorrhage\n- Occasional epistaxis\n- Severe spontaneous haemorrhages: uncommon\n- Prolonged aPTT in laboratory tests without apparent clinical signs

Factor XI deficiency has been known for decades in human medicine and has been described in several domestic species, including the cat, through clinical cases with prolonged aPTT and specific factor activity assays. The association with the Maine Coon and the availability of the DNA test are recent additions to feline panels. Frequency data in the breed remain scarce.

- Test Maine Coon breeding animals, especially if there is a history of bleeding in the line.\n- Do not cross two carriers: on average, 25% of the litter would be affected.\n- A carrier can be crossed with a clear cat and the offspring intended for breeding tested.\n- If an affected cat needs surgery, plan it with the veterinarian (plasma reserve, local haemostatic measures) and avoid drugs that interfere with haemostasis.

Differential diagnosis with other feline coagulopathies: factor XII deficiency (very common in cats, prolonged aPTT without bleeding risk) and von Willebrand disease. Functional confirmation is the measurement of factor XI activity. In affected cats, non-steroidal anti-inflammatory drugs and anticoagulants should be avoided; in carriers, special precautions are usually not required.

1. Kuder H, Dickeson SK, Brooks MB, Kehl A, Müller E, Gailani D, Giger U. 2022. A common missense variant causing factor XI deficiency and increased bleeding tendency in Maine Coon cats (Genes, Basel) (PMID 35627175).
2. OMIA:000363-9685 (Factor XI deficiency, F11, Felis catus).