A 4-year-old child from a rural area presents with a history of difficulty seeing at dusk for several months. Examination shows dry, wrinkled conjunctiva with a foamy white triangular deposit on the temporal limbus. Which vitamin deficiency is most likely responsible?
- A Thiamine
- B Riboflavin
- C Vitamin A ✓
- D Ascorbic acid
Correct answer: C. Vitamin A
Explanation
Night blindness is the earliest manifestation of vitamin A deficiency because retinal (11-cis-retinal) is required to regenerate rhodopsin in rod cells. The foamy triangular conjunctival deposit described is a Bitot spot, a classic sign of xerophthalmia caused by keratinizing squamous metaplasia of the conjunctival epithelium. Thiamine deficiency causes beriberi, riboflavin causes angular stomatitis, and ascorbic acid deficiency causes bleeding gums and poor wound healing, none of which produce night blindness.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.