A patient maintained on total parenteral nutrition (TPN) develops peripheral neuropathy, confusion, and lactic acidosis after 3 weeks. Deficiency of which micronutrient explains all three features?

• A Thiamine (vitamin B1) — required as a coenzyme for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, and as transketolase cofactor for nerve function ✓
• B Zinc — required for superoxide dismutase and peripheral nerve myelin maintenance
• C Biotin — required for multiple carboxylation reactions including pyruvate carboxylase
• D Selenium — required for glutathione peroxidase; its deficiency causes oxidative neuronal damage

Explanation

TPN solutions may lack adequate thiamine unless supplemented. Thiamine (B1) as thiamine pyrophosphate (TPP) is the coenzyme for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. Deficiency impairs pyruvate oxidation causing lactic acidosis, impairs TCA cycle function causing neuronal energy failure (confusion/encephalopathy), and causes Wernicke's encephalopathy. Peripheral neuropathy from thiamine deficiency manifests as dry beriberi. Biotin deficiency causes organic aciduria but is rare and not the same triad.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.