A deficiency in which compound leads to increased clotting time and may cause hemorrhagic disease in infancy?

A deficiency in which compound leads to increased clotting time and may cause hemorrhagic disease in infancy?

• A. Riboflavin
• B. Pyridoxine
• C. Tocopherols
• D. Menaquinone

Answer: (D)

Vitamin K–dependent gamma-carboxylation is essential for activating clotting factors II, VII, IX, and X (and proteins C and S). Without sufficient vitamin K, these factors can’t bind calcium properly, so the coagulation cascade is impaired, leading to longer clotting times and a risk of bleeding. In infancy, hemorrhagic disease can occur because newborns have low stores of vitamin K and their gut bacteria that produce vitamin K are not yet established. Menaquinone is vitamin K2, the bacterial form of vitamin K, and its deficiency disrupts the necessary carboxylation of those clotting factors, producing the bleeding tendency. The other vitamins listed aren’t involved in this gamma-carboxylation step, so they don’t cause the same neonatal coagulation disorder.

Vitamin K–dependent gamma-carboxylation is essential for activating clotting factors II, VII, IX, and X (and proteins C and S). Without sufficient vitamin K, these factors can’t bind calcium properly, so the coagulation cascade is impaired, leading to longer clotting times and a risk of bleeding. In infancy, hemorrhagic disease can occur because newborns have low stores of vitamin K and their gut bacteria that produce vitamin K are not yet established. Menaquinone is vitamin K2, the bacterial form of vitamin K, and its deficiency disrupts the necessary carboxylation of those clotting factors, producing the bleeding tendency. The other vitamins listed aren’t involved in this gamma-carboxylation step, so they don’t cause the same neonatal coagulation disorder.