This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
A 40 year old male patient complains of diminished vision during night and dryness of eyes. Patient gives history of recurrent bacterial infections. The plasma level of retinol binding protein in this patient will be: 
Select and explain. 
A. Decreased, B. Increased, C. Unchanged, D. Fluctuating
A: Decreased
Answer: A: Decreased 
Explanation: Night blindness (nyctalopia) is one of the earliest symptoms of vitamin A deficiency. Severe deficiency of vitamin A leads to xerophthalmia. The plasma level of retinol binding protein is decreased in vitamin A deficiency.
Satyanarayana- Biochemistry, 3rd edition, pg-123