What is the effect of Vitamin K (Vitamin K) deficiency on coagulation factors?

Vitamin K Deficiency and Coagulation Factors

Vitamin K deficiency causes deficiencies of functional forms of coagulation factors II, VII, IX, and X (answer B).

Mechanism of Vitamin K in Coagulation

Vitamin K serves as an essential cofactor in the post-translational modification of specific coagulation factors. Its primary role in hemostasis involves:

• Acting as a cofactor for a microsomal enzyme that catalyzes the carboxylation of glutamic acid residues to gamma-carboxyglutamic acid (Gla) in inactive hepatic precursors 1
• This carboxylation is critical for factors II (prothrombin), VII, IX, and X to bind calcium and attach to phospholipid surfaces 2
• Without this carboxylation, these factors cannot participate effectively in the blood coagulation cascade 1

Effects of Vitamin K Deficiency

When vitamin K is deficient, the following occurs:

• Production of non-functional or undercarboxylated forms of factors II, VII, IX, and X 3
• These undercarboxylated factors (also called PIVKA - Proteins Induced by Vitamin K Absence or Antagonism) cannot bind calcium effectively 1
• Without calcium binding, these factors cannot attach to phospholipid surfaces and participate in coagulation 2
• The result is prolongation of prothrombin time and impaired clotting ability 3

Why Other Options Are Incorrect

• Option A (true deficiency of antithrombin): Vitamin K deficiency does not cause antithrombin deficiency. Antithrombin is not a vitamin K-dependent protein.
• Option C (deficiencies of functional forms of fibrinogen and factor VIII): Fibrinogen and factor VIII are not vitamin K-dependent factors, so their function is not directly affected by vitamin K deficiency 4.
• Option D (liver disease): While liver disease can cause coagulopathy and may affect vitamin K metabolism, vitamin K deficiency itself does not cause liver disease 3.

Common Causes of Vitamin K Deficiency

• Fat malabsorption conditions (celiac disease, cystic fibrosis, short bowel syndrome) 3
• Malnutrition 3
• Prolonged antibiotic therapy (disrupts gut flora that produces vitamin K2) 3
• Anticoagulant therapy with vitamin K antagonists (e.g., warfarin) 3
• Neonates (limited hepatic storage) 3

Clinical Manifestations

• Bleeding tendency, which can range from mild to severe 3
• Prolonged prothrombin time (PT) 3
• Normal partial thromboplastin time (unless factors IX and X are severely decreased) 5
• Potentially fatal bleeding, especially in newborns 1

Diagnosis

• Measurement of PIVKA-II (protein induced by vitamin K absence or antagonism-II) - a sensitive biomarker of hepatic subclinical vitamin K deficiency 3
• Prothrombin time and other coagulation tests 3
• Response to vitamin K administration (correction of coagulopathy within 12-24 hours) 2

Treatment

• Vitamin K administration (oral or parenteral) 2
• IV administration has maximum effect in 6-12 hours 3
• Oral supplementation takes about 24 hours for full effect 3
• For severe bleeding, prothrombin complex concentrate may be used alongside vitamin K 3

Prevention

• Adequate dietary intake (leafy greens, cruciferous vegetables, etc.) 3
• Vitamin K prophylaxis in newborns 5
• Monitoring patients on antibiotics or with malabsorption 3

In conclusion, vitamin K deficiency specifically affects the vitamin K-dependent coagulation factors (II, VII, IX, and X), resulting in the production of non-functional forms of these proteins and subsequent coagulopathy.