Correct Answer: B. Thiamine
Thiamine (Vitamin B1) deficiency causes beriberi, a disease with two cardinal presentations: wet beriberi (high-output cardiac failure with peripheral edema) and dry beriberi (peripheral neuropathy). The cardiac manifestation occurs because thiamine is essential for pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes in the citric acid cycle. Without adequate thiamine, pyruvate accumulates, leading to lactic acidosis and impaired myocardial energy production, resulting in dilated cardiomyopathy and high-output heart failure with characteristic peripheral edema. The neuropathy (dry beriberi) develops due to thiamine's role in transketolase activity; deficiency impairs pentose phosphate pathway function, reducing NADPH production needed for myelin synthesis and nerve conduction. In India, thiamine deficiency remains endemic in populations consuming polished rice without fortification, particularly in rural areas and among malnourished children. The combination of cardiac edema AND neuropathy in a single deficiency state is pathognomonic for thiamine deficiency—no other B vitamin causes both manifestations simultaneously.
Why the other options are wrong
A. Pyridoxine — Pyridoxine (B6) deficiency causes peripheral neuropathy and dermatitis (seborrheic rash around eyes and mouth), but does NOT cause cardiac edema or high-output heart failure. It is involved in transamination and neurotransmitter synthesis, not myocardial energy metabolism. The absence of cardiac involvement rules this out. C. Biotin — Biotin deficiency is rare and causes dermatitis, alopecia, and neurological symptoms, but cardiac edema is not a recognized manifestation. Biotin's role in carboxylase enzymes does not directly impact myocardial function or cause the high-output heart failure seen in beriberi. D. Riboflavin — Riboflavin (B2) deficiency causes ariboflavinosis with angular cheilitis, glossitis, and seborrheic dermatitis, but does NOT cause cardiac edema or peripheral neuropathy. While riboflavin is a cofactor in FAD-dependent enzymes, its deficiency does not produce the characteristic beriberi syndrome.
High-Yield Facts
- Beriberi = thiamine deficiency with two forms: wet (cardiac edema, high-output heart failure) and dry (peripheral neuropathy, Wernicke-Korsakoff in severe cases).
- Wet beriberi presents with dilated cardiomyopathy, peripheral edema, and pulmonary congestion due to impaired pyruvate metabolism and myocardial energy depletion.
- Dry beriberi manifests as distal symmetrical peripheral neuropathy (stocking-glove distribution) from impaired transketolase and pentose phosphate pathway dysfunction.
- Thiamine's biochemical role: essential cofactor for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase—deficiency disrupts both energy metabolism and myelin synthesis.
- Indian epidemiology: thiamine deficiency endemic in populations consuming polished rice without fortification; common in malnourished children and alcoholics.
Mnemonics
WET vs DRY Beriberi Wet = heart (Water retention, edema, Cardiac failure); Dry = nerves (Dry neuropathy, Distal weakness). Remember: wet = wet with fluid (cardiac), dry = dry nerves (neuropathy). B Vitamins & Their Syndromes B1 (Thiamine) = Beriberi (cardiac + neuro); B2 (Riboflavin) = Ariboflavinosis (cheilitis); B3 (Niacin) = Pellagra (4 Ds: diarrhea, dermatitis, dementia, death); B6 (Pyridoxine) = Neuropathy + dermatitis (no cardiac).
NBE Trap
NBE may pair "neuropathy" with pyridoxine deficiency (which does cause neuropathy) to distract from the discriminating feature: only thiamine deficiency causes BOTH cardiac edema AND neuropathy together. Students who focus solely on neuropathy without recognizing the cardiac component will select pyridoxine.
Clinical Pearl
In rural India, a malnourished child presenting with both peripheral edema and distal neuropathy should raise immediate suspicion for thiamine deficiency beriberi—especially if there is a history of polished rice consumption without fortification. Early thiamine supplementation (10–50 mg daily) can reverse wet beriberi's cardiac manifestations within days, but dry beriberi's neuropathy may take weeks to months to resolve.
_Reference: Harrison Ch. 75 (Vitamin Deficiencies); Robbins Ch. 9 (Nutritional Pathology); OP Ghai Ch. 4 (Malnutrition and Vitamin Deficiencies)_