Hereditary defect of the intrinsic coagulation pathway due to factor XI deficiency. It produces mild to moderate bleeding diathesis, with prolonged bleeding after surgery, trauma or from mucosae, but usually does not cause severe spontaneous haemorrhage. Severity is variable between individuals. It is inherited in a recessive manner with variable expressivity.

Specific to the kerry blue terrier. No reliable carrier frequencies are published in the general population; data are limited and concentrate in related lines.

- Prolonged bleeding after surgery or trauma
- Mucosal bleeding (gums, epistaxis)
- Easy bruising
- Prolonged aPTT with normal prothrombin time
- Spontaneous haemorrhage is uncommon

Factor XI deficiency was recognised in the kerry blue terrier from cases of postoperative bleeding not attributable to other coagulopathies. Molecular studies associated it with a variant of the F11 gene that reduces factor activity. Its characterisation enabled a genetic carrier test used in breeding the breed, especially before surgical procedures.

- Test breeding dogs before mating
- Do not mate two carriers: 25 % risk of homozygotes
- A carrier can be mated to a clear dog; test the offspring intended for breeding
- Know the status of homozygotes before surgery or bleeding procedures
- Avoid spreading the allele to lines where it does not exist

Differential diagnosis with other coagulopathies of the intrinsic pathway (haemophilia A/B, factor XII deficiency, prekallikrein deficiency) and with thrombopathies. Variable severity means factor XI levels do not reliably predict bleeding risk. Before surgery in homozygotes, foresee fresh frozen plasma and strict haemostatic management.

1. Knowler C, Giger U, Dodds WJ, Brooks M. 1994, Factor XI deficiency in Kerry Blue Terriers. J Am Vet Med Assoc 205(11):1557-61. PMID: 7730123. 2. OMIA:000363-9615 (Factor XI deficiency; variante SINE del exón 7, descrita por Tcherneva et al. 2007, no indexada en PubMed).