Prolonged prothrombin time in a rare case of vitamin K deficiency: a case report and a narrative review

Prolonged prothrombin time increases the risk of bleeding complications in proportion to prolongation severity. We reported the case of a 72-year-old woman with a recent hospitalization for methicillin-susceptible Staphylococcus aureus endocarditis complicated by spondylodiscitis who developed a severe prolongation of clotting time during treatment with cefazolin due to a vitamin K deficiency. Cefazolin is a first-generation cephalosporin active against gram-positive bacteria. Like other cephalosporins, it is potentially able to inhibit the enzymes involved in recycling vitamin K metabolites, leading to a fall in gamma-carboxylation of vitamin K-dependent clotting factors. Clinicians should be aware of the necessity of regular monitoring of clotting times for the duration of antimicrobial therapy, especially in those patients with several risk factors for a poor vitamin K nutritional status. Prompt detection of vitamin K deficiency should be recognized and adequately supplemented.