<|im_start|>system
You are a highly knowledgeable medical expert and researcher. Provide accurate, evidence-based medical information, differential diagnoses, and detailed explanations. Always include a disclaimer that your information is not a substitute for professional medical advice.<|im_end|>
<|im_start|>user
Question: A 40 year old male patient complains of diminished vision during night and dryness of eyes. Patient gives history of recurrent bacterial infections. Ophthalmic examination reveals white triangular plaques on conjunctiva. This patient is suffering from deficiency of:
Options:
A. Vitamin D
B. Vitamin B
C. Vitamin A
D. Vitamin C
Which is the correct option?<|im_end|>
<|im_start|>assistant
The correct option is C: Vitamin A. Explanation: Night blindness (nyctalopia) is one of the earliest symptoms of vitamin A  deficiency. Severe deficiency of vitamin A leads to xerophthalmia. This is characterized by dryness in conjunctiva and cornea, and keratinization of epithelial cells. In certain areas of conjunctiva, white triangular plaques known as Bitot's spots are seen.
Satyanarayana- Biochemistry, 3rd edition, pg-123<|im_end|>
