A patient with exclusive parenteral nutrition (PN) for 3 months develops peripheral neuropathy. Plasma pyruvate is elevated. The vitamin deficiency most likely responsible is:

• A Riboflavin (B2)
• B Pyridoxine (B6)
• C Cobalamin (B12)
• D Thiamine (B1) ✓

Explanation

Thiamine pyrophosphate (TPP) is the coenzyme for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase, and branched-chain alpha-keto acid dehydrogenase. Thiamine deficiency blocks PDH, causing pyruvate accumulation and lactic acidosis. PN formulations historically sometimes omitted thiamine, causing iatrogenic Wernicke's encephalopathy and peripheral neuropathy. Elevated plasma pyruvate with normal or elevated lactate on PN should trigger immediate thiamine supplementation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.