A 4-year-old boy from a rural area presents with difficulty seeing at dusk. Examination shows foamy, triangular plaques of keratinized epithelium on the temporal bulbar conjunctiva. This finding is characteristic of deficiency of which vitamin?

• A Thiamine
• B Riboflavin
• C Vitamin A ✓
• D Vitamin C

Explanation

The foamy triangular plaque on the bulbar conjunctiva is a Bitot spot, a hallmark of vitamin A deficiency caused by squamous metaplasia of the conjunctival epithelium. Night blindness is the earliest functional sign because retinal is required for rhodopsin regeneration in rods. Progression leads to corneal xerosis and keratomalacia. Riboflavin deficiency causes corneal vascularization rather than keratinized plaques, and vitamin B deficiency causes gingival bleeding, so both are excluded by the specific ocular lesion described.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.