Abstract
Background:
Vitamin K is a member of the fat-soluble vitamins group and plays a key role in hemostasis by facilitating the activation of vitamin K-dependent clotting factors and contributing to the synthesis of various coagulation proteins. Consequently, its antagonization or deficiency, secondary to reduced production or malabsorption impairs coagulation, leads to an increased risk of bleeding.

Case Description:
A 4-year-old, intact female German Shepherd was referred for a year-long history of anorexia, intermittent vomiting, and chronic diarrhea. Over the past two days, she developed oral bleeding. Diagnostic investigations revealed markedly prolonged prothrombin (PT) and activated partial thromboplastin times (aPTT), with normal plasma fibrinogen levels. These findings, in conjunction with the normalization of PT and aPTT following vitamin K1 administration and the exclusion of rodenticide or coumarins intoxication, were suggestive of vitamin K deficiency secondary to intestinal malabsorption. Further investigations led to the diagnosis of severe lymphoplasmacytic enterocolitis.

Conclusion:
Vitamin K-responsive coagulopathy associated with malabsorption syndrome secondary to lymphocytic-plasmacytic enteritis has been previously described in two cats, but this is the first report of its occurrence in a dog. Therefore, vitamin K treatment should be considered in all animals with intestinal malabsorption.

Key words: Vitamin K, Coagulation, Lymphocytic-plasmacytic enteritis, Dog