Correct Answer: C. Thiamine
Thiamine (vitamin B1) deficiency presents with a classic triad of peripheral edema, cardiac involvement (cardiomegaly), and mucosal changes. The combination of pedal edema + cheilosis + cardiomegaly is pathognomonic for wet beriberi, the acute cardiac form of thiamine deficiency. Thiamine is an essential cofactor for pyruvate dehydrogenase and transketolase; its deficiency impairs carbohydrate metabolism, leading to lactate accumulation and metabolic acidosis. This triggers high-output cardiac failure with peripheral vasodilation, causing edema and cardiomegaly. Cheilosis (angular cheilitis, cracked lips) occurs due to impaired epithelial regeneration. In India, thiamine deficiency is endemic in populations consuming polished rice without fortification, particularly in rural areas and among malnourished children. The acute presentation with cardiac decompensation (wet beriberi) is a medical emergency requiring immediate thiamine replacement (10–20 mg IV/IM daily). Chronic deficiency presents as dry beriberi with neuropathy, but the acute cardiac presentation with edema is the discriminating feature here.
Why the other options are wrong
A. Niacin — Niacin deficiency causes pellagra (dermatitis, diarrhea, dementia, death—the 4 Ds), not cardiomegaly or pedal edema. Pellagra presents with photosensitive dermatitis on sun-exposed areas and glossitis, not cheilosis. Cardiomegaly is not a feature of niacin deficiency. B. Riboflavin — Riboflavin deficiency causes ariboflavinosis, presenting with angular cheilitis, glossitis, and seborrheic dermatitis—but NOT cardiomegaly or pedal edema. While cheilosis may overlap, the absence of cardiac involvement rules out riboflavin. Riboflavin is not cardiotoxic. D. Pyridoxine — Pyridoxine (B6) deficiency causes peripheral neuropathy, seizures, and dermatitis, not cardiomegaly or edema. It does not produce the acute high-output cardiac failure seen in thiamine deficiency. Pyridoxine is not involved in pyruvate metabolism or lactate accumulation.
High-Yield Facts
- Wet beriberi = acute thiamine deficiency with cardiomegaly, high-output heart failure, and pedal edema; dry beriberi = chronic thiamine deficiency with peripheral neuropathy and Wernicke–Korsakoff syndrome.
- Thiamine cofactor role: pyruvate dehydrogenase and transketolase; deficiency → lactate accumulation → metabolic acidosis → vasodilation and cardiac failure.
- Cheilosis (angular cheilitis) is a nonspecific mucosal sign seen in both thiamine and riboflavin deficiency, but cardiomegaly is pathognomonic for thiamine deficiency among B vitamins.
- Indian epidemiology: thiamine deficiency endemic in polished-rice-consuming populations; fortification of rice is key prevention strategy per FSSAI guidelines.
- Emergency treatment: IV/IM thiamine 10–20 mg daily; oral replacement inadequate in acute beriberi due to malabsorption and cardiac decompensation.
Mnemonics
WET BERIBERI = Thiamine Weak heart (cardiomegaly), Edema (pedal), Tachycardia → Thiamine deficiency. Remember: wet = cardiac, dry = neurologic. B-Vitamin Cardiac Link Only Thiamine causes cardiomegaly among B vitamins. Niacin → pellagra (4 Ds), Riboflavin → cheilitis alone, Pyridoxine → neuropathy.
NBE Trap
NBE pairs cheilosis with riboflavin to distract; students who focus only on mucosal signs miss that cardiomegaly is the discriminating feature unique to thiamine deficiency. The combination of three signs (edema + cheilosis + cardiomegaly) is the key to avoiding the riboflavin trap.
Clinical Pearl
In Indian pediatric practice, a malnourished child presenting with acute-onset pedal edema and cardiomegaly should raise immediate suspicion for wet beriberi—a medical emergency requiring stat IV thiamine before investigations. Many rural Indian children on exclusive polished-rice diets present this way; early recognition prevents sudden cardiac death.
_Reference: KD Tripathi Pharmacology Ch. 48 (Vitamins); Robbins Pathology Ch. 8 (Nutritional Deficiencies); Harrison Principles of Internal Medicine Ch. 75 (Vitamin Deficiencies)_