Correct Answer: B. Vitamin K
The medication inhibits fat absorption, leading to malabsorption of fat-soluble vitamins (A, D, E, K). The clinical presentation of easy bruising and increased menstrual bleeding points directly to a coagulation defect. Vitamin K is the essential cofactor for hepatic synthesis of prothrombin (Factor II), Factor VII, Factor IX, and Factor X—the vitamin K-dependent clotting factors. Without adequate vitamin K, these factors cannot be γ-carboxylated, resulting in impaired thrombin generation and prolonged PT/INR. Easy bruising reflects spontaneous bleeding into skin and subcutaneous tissues; menorrhagia occurs due to defective hemostasis in the endometrium. This is a classic presentation of vitamin K deficiency, which commonly occurs with fat malabsorption (celiac disease, cystic fibrosis, post-bariatric surgery, or as here, with lipase inhibitors like orlistat). The deficiency manifests within weeks because vitamin K has minimal body stores and depends on continuous dietary intake and bacterial synthesis in the colon. In Indian clinical practice, vitamin K deficiency is recognized as a complication of prolonged antibiotic use, diarrheal illnesses, and malabsorptive states—all common in our population. The diagnosis is confirmed by elevated PT/INR with normal platelet count and bleeding time, and corrected by vitamin K supplementation (phytonadione 10 mg IV/IM).
Why the other options are wrong
A. Vitamin D — Vitamin D deficiency causes hypocalcemia, leading to tetany, seizures, and bone pain—not bleeding diathesis. While vitamin D is fat-soluble and can be malabsorbed, it does not directly affect coagulation. Easy bruising and menorrhagia are not features of vitamin D deficiency. This is a distractor that exploits knowledge of fat-soluble vitamin malabsorption but misses the specific bleeding phenotype. C. Vitamin E — Vitamin E deficiency causes neurological manifestations (ataxia, neuropathy, ophthalmoplegia) and hemolytic anemia, not coagulation defects. Although vitamin E is fat-soluble and malabsorbed with the medication, it has no role in the intrinsic or extrinsic coagulation cascade. The bleeding presentation here is incompatible with vitamin E deficiency, making this a plausible but incorrect distractor. D. Vitamin B6 — Vitamin B6 (pyridoxine) is water-soluble, not fat-soluble, and therefore is NOT malabsorbed by fat-absorption inhibitors. B6 deficiency causes peripheral neuropathy, anemia, and dermatitis—not bleeding. This option exploits confusion about vitamin classification and is a clear trap for students who do not recall that B vitamins are water-soluble.
High-Yield Facts
- Vitamin K-dependent factors: Factors II, VII, IX, X (mnemonic: 2, 7, 9, 10) require γ-carboxylation for function; deficiency prolongs PT/INR.
- Fat-soluble vitamin malabsorption: Vitamins A, D, E, K are absorbed with dietary fat; lipase inhibitors (orlistat), celiac disease, and cystic fibrosis cause deficiency within weeks.
- Vitamin K deficiency bleeding phenotype: Easy bruising, menorrhagia, GI bleeding, and epistaxis; platelet count and bleeding time are normal (coagulation defect, not thrombocytopenia).
- Vitamin K body stores: Minimal hepatic reserves; deficiency manifests rapidly (2–7 days) because dietary intake and colonic bacterial synthesis are the only sources.
- Treatment: Phytonadione (vitamin K1) 10 mg IV/IM corrects PT/INR within 12–24 hours; oral supplementation takes 24–72 hours.
Mnemonics
PIVKA (Proteins Induced by Vitamin K Absence) When vitamin K is deficient, the liver produces Prothrombin, Factor VII, IX, and X that are Uncarboxylated and Non-functional. These appear in serum as PIVKA and prolong PT. Use this when you see bleeding + normal platelets + elevated PT. 2-7-9-10 Rule Vitamin K-dependent factors are 2 (prothrombin), 7, 9, and 10. These are the only four factors that require γ-carboxylation. Memorize this sequence to quickly identify vitamin K deficiency as the cause of prolonged PT.
NBE Trap
NBE pairs fat-soluble vitamin malabsorption with vitamin D and E to distract from the specific coagulation phenotype (easy bruising + menorrhagia). Students who know "fat-soluble vitamins are malabsorbed" may pick D or E without linking the bleeding presentation to vitamin K's unique role in the coagulation cascade.
Clinical Pearl
In Indian practice, vitamin K deficiency is commonly seen in patients with chronic diarrhea (infectious or inflammatory), those on prolonged antibiotics (which suppress colonic bacteria), and increasingly in those using weight-loss supplements. A simple PT/INR test and rapid response to parenteral vitamin K (within 24 hours) confirm the diagnosis and guide management—critical in preventing life-threatening hemorrhage.
_Reference: KD Tripathi Ch. 32 (Vitamins); Harrison Ch. 140 (Coagulation Disorders); Robbins Ch. 4 (Hemostasis)_