Canine Prekallikrein Deficiency
Canine prekallikrein deficiency is a rare inherited disorder characterized by prolonged clotting time. The disorder is affecting the Shih Tzu dog breed. Except in dogs, the disorder has been diagnosed in human patients and Miniature and Belgian horses. Identification of the causative mutation in the affected Shih Tzus has enabled identification of clear, carrier and affected dogs for the disorder.
Characteristics and Symptoms
Prekallikrein (PK), or the Fletcher factor, is a serum protein which is homologous to factor XI. It modulates the activation of factor XI and factor XII , two important factors in the clotting process. When activated, prekallikrein forms its activated form kallikrein, which participates in the regulation of blood pressure and activation of inflammation. When prekallikrein is deficient, factor XII is activated more slowly which results in prolonged clotting time in case of injury.
Clinical signs in affected dogs are usually absent but hematuria (the presence of blood in the urine), gastrointestinal hemorrhage and excessive postoperative bleeding can occur. The dog may get bruises easily and have frequent nosebleeds. Since the symptoms are mild and may be not evident until performed surgery or trauma occurs, affected dog can remain unidentified until excessive prolonged clotting time is not revealed. This is especially dangerous in case of a needed surgery. When performing a needed surgery of prekallikrein deficient dog, veterinarians should have a ready access to blood banks for transfusion.
Canine prekallikrein deficiency is caused by a point mutation in the KLKB1 gene. The disorder is inherited in an autosomal recessive pattern. Healthy parents of an affected dog are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes have no symptoms. At conception, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Chinn DR et al (1986) Prekallikrein deficiency in a dog. J Am Vet Med Assoc 188(1):69-71