Identification of an F13A1 frameshift variant associated with factor XIII deficiency in a Coonhound dog with severe coagulopathy.

FXIII deficiency should be considered in dogs with severe bleeding and normal standard coagulation screening results.

This case report describes the identification of a novel F13A1 frameshift variant causing Factor XIII (FXIII) deficiency in a 4-month-old male Black and Tan Coonhound. The dog presented with spontaneous hemoperitoneum, thrombocytopenia, and persistent post-surgical hemorrhage. FXIII is a transglutaminase that crosslinks fibrin polymers to stabilize clot architecture; deficiency results in mechanically fragile clots and severe hemorrhagic diathesis. Comprehensive hemostasis testing confirmed functional FXIII deficiency, and whole genome sequencing identified a private homozygous variant (c.1234_1239delinsTCAA) in exon 11 of the F13A1 gene, predicting a frameshift and premature stop codon consistent with a loss-of-function mechanism. This mirrors the autosomal recessive inheritance pattern observed in human FXIII deficiency. Notably, standard coagulation screening tests (PT, aPTT) are typically normal in FXIII deficiency, making specific FXIII activity assays essential for diagnosis. This represents only the second clinical report of FXIII deficiency in dogs and the first genetic characterization of any canine or companion animal FXIII deficiency. The identified variant enables development of a breed-specific genetic test for Black and Tan Coonhounds, facilitating carrier detection and informed breeding decisions. Clinicians encountering unexplained severe bleeding with normal standard coagulation panels in dogs should consider FXIII deficiency in their differential diagnosis, particularly in this breed.

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