Hemophilia B is a hereditary X-linked coagulopathy caused by deficiency of factor IX of the intrinsic coagulation pathway. A severe form associated with the F9 c.731G>A p.(G244E) mutation has been described in the Rhodesian Ridgeback. Affected males present spontaneous bleeding or bleeding disproportionate to trauma and surgery; carrier females are usually asymptomatic. DNA testing identifies carriers and allows breeding planning.

Applicable breed: Rhodesian Ridgeback. No reliable carrier frequencies have been published (limited data).

- Prolonged bleeding after trauma, surgery or tooth extraction\n- Spontaneous or easily appearing hematomas\n- Hemarthroses and deep muscle hemorrhages\n- Severe hemorrhage after invasive procedures\n- In affected males, hemorrhagic picture from an early age\n- Carrier females: usually asymptomatic

Mischke and co-workers (2011) described severe hemophilia B in the Rhodesian Ridgeback caused by the p.(G244E) substitution of the F9 gene. OMIA includes hemophilia B and the breed-specific variant (OMIA:000438-9615).

- Test breeding dogs: in the female, genetic testing identifies carriers; in the affected male, the diagnosis is clinical and molecular.\n- A carrier female should not be mated to an affected male (risk of affected offspring in both sexes).\n- Daughters of an affected male are inevitably carriers: do not use them for breeding without counselling.\n- Affected males should not be used for reproduction.\n- Select offspring free of the variant to progressively replace carrier lines.

Prolonged aPTT with normal PT; measurement of factor IX activity and genetic testing confirm the diagnosis. Differential diagnosis with hemophilia A (factor VIII) and von Willebrand disease. In affected males, any surgery must be planned with hemostatic support (plasma, factor IX).

1. Mischke R, Kühnlein P, Kehl A, Langbein-Detsch I, Steudle F, Schmid A, Dandekar T, Czwalinna A, Müller E. 2011. G244E in the canine factor IX gene leads to severe haemophilia B in Rhodesian Ridgebacks (Vet J) (PMID 20303304).
2. OMIA:000438-9615 (Haemophilia B, F9, Canis lupus familiaris).