A 15-year-old boy is brought to the emergency department with fever, purulent nasal discharge, and epistaxis. The patient has had fever and persistent nasal discharge for the past 10 days. He developed intermittent epistaxis 2 days ago that has been difficult to control. The patient has also had easy bruising for the past 2 months. Medical history is significant for cystic fibrosis, and he has not been taking his prescribed medications. Results of coagulation studies are as follows: Which of the following coagulation factors is most likely to be abnormal in this patient?

Question

A 15-year-old boy is brought to the emergency department with fever, purulent nasal discharge, and epistaxis.  The patient has had fever and persistent nasal discharge for the past 10 days.  He developed intermittent epistaxis 2 days ago that has been difficult to control.  The patient has also had easy bruising for the past 2 months.  Medical history is significant for cystic fibrosis, and he has not been taking his prescribed medications.  Results of coagulation studies are as follows:  Which of the following coagulation factors is most likely to be abnormal in this patient?

Quizplus · Accepted Answer

11ec160b_3afb_6d4c_9249_09f7d4babd43_MD0001_00 This patient with cystic fibrosis (CF) has bruising, epistaxis, and a prolonged PT, findings consistent with vitamin K deficiency. Patients with CF are at increased risk due to a predisposition to pancreatic insufficiency, in which viscous exocrine secretions block pancreatic ducts. Reduced secretion of pancreatic enzymes leads to fat malabsorption and deficiency of fat-soluble vitamins (ie, A, D, E, K). Vitamin K normally acts as an important cofactor in the hepatic activation of coagulation factors II, VII, IX, and X, as well as proteins C and S. Vitamin K deficiency results in low levels of activated vitamin K-dependent coagulation factors, and prolonged PT is caused by deficiency of activated factor VII. Activated PTT (aPTT) is typically normal, as seen in this patient, although it can be prolonged with severe vitamin K deficiency (due to the effect on factor II). Vitamin K deficiency presents with easy bruising and mucosal bleeding (eg, epistaxis). Treatment is vitamin K administration, and patients with CF also should receive pancreatic enzyme replacement therapy to improve fat-soluble vitamin absorption. (Choice A) Factor V is not dependent on vitamin K for activation. Factor V deficiency is rare and leads to prolonged PT and aPTT. (Choice C) Hemophilia A is an X-linked recessive disorder caused by factor VIII deficiency. As part of the intrinsic pathway, factor VIII deficiency results in prolongation of aPTT with normal PT. (Choice D) Factor XII (ie, Hageman factor) is part of the intrinsic coagulation pathway and is not vitamin K dependent. Patients with inherited factor XII deficiency are typically asymptomatic but have prolonged aPTT. (Choice E) Fibrinogen normally assists in coagulation via the final common pathway through fibrin clot formation and platelet binding. Fibrinogen is not dependent on vitamin K for activation. Coagulation disorders involving fibrinogen include severe liver disease and disseminated intravascular coagulation, which are associated with prolonged PT and aPTT. Educational objective: Patients with cystic fibrosis are at risk for fat-soluble vitamin (ie, A, D, E, K) deficiency due to fat malabsorption from pancreatic insufficiency. Vitamin K is an important cofactor in the activation of coagulation factors II, VII, IX, and X. Vitamin K deficiency leads to easy bruising, mucosal bleeding, and prolonged PT.

A 15-Year-Old Boy Is Brought to the Emergency Department with Fever