## Identifying the Incorrect Statement **Key Point:** Vitamin K is essential for the synthesis of **clotting factors II, VII, IX, and X** (the vitamin K-dependent factors), NOT factor V. Factor V is synthesized in the liver but is **not vitamin K-dependent**; it is a cofactor in the prothrombinase complex. ## Fat-Soluble Vitamins: Deficiency Features | Vitamin | Deficiency Manifestations | Biochemical Role | |---------|---------------------------|------------------| | **A** | Night blindness (early), xerophthalmia, Bitot's spots, follicular hyperkeratosis, keratomalacia | Synthesis of 11-cis retinal for rhodopsin; epithelial differentiation | | **D** | Rickets (children), osteomalacia (adults), hypocalcemia, secondary hyperparathyroidism | Calcium and phosphate absorption; bone mineralization | | **E** | Spinocerebellar degeneration, hemolytic anemia (premature infants), peripheral neuropathy | Antioxidant; protects cell membranes from lipid peroxidation | | **K** | Bleeding tendency, prolonged PT/INR, defective synthesis of factors **II, VII, IX, X** | γ-carboxylation of vitamin K-dependent clotting factors | **High-Yield:** **Mnemonic for vitamin K-dependent factors:** **"PIVKA"** = Prothrombin (II), Proconvertin (VII), Christmas factor (IX), Stuart factor (X). Factor V is **NOT** in this group. ## Clinical Pearl **Warning:** A common NEET PG trap is listing factor V as vitamin K-dependent. Factor V is synthesized in the liver but does NOT require vitamin K for its synthesis. It is deficient in severe liver disease and disseminated intravascular coagulation (DIC), but NOT specifically in vitamin K deficiency. **Tip:** When you see a question about vitamin K deficiency and clotting factors, immediately think **"2, 7, 9, 10"** or use the PIVKA mnemonic. If factor V is mentioned as vitamin K-dependent, it is a distractor. [cite:Harrison 21e Ch 140]
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