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:
## **Core Concept**
The patient's symptoms suggest a condition related to vitamin A deficiency, which affects night vision and can cause dryness of the eyes (xerophthalmia). Vitamin A is crucial for the synthesis of rhodopsin, a pigment necessary for night vision. Additionally, recurrent bacterial infections hint at an immune system dysfunction, which can be related to zinc deficiency or a condition affecting the immune system.
## **Why the Correct Answer is Right**
Vitamin A binds to retinol-binding protein (RBP) in the plasma for transport to target tissues. In conditions of vitamin A deficiency or when there is an increased utilization of vitamin A (such as in infections), the levels of retinol-binding protein can decrease. This decrease reflects the body's attempt to prioritize the use of available vitamin A. Therefore, in a patient with symptoms suggestive of vitamin A deficiency and recurrent infections, the plasma level of retinol-binding protein would likely be decreased.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests an increased level of retinol-binding protein, which would not align with a deficiency state or increased utilization of vitamin A.
- **Option B:** This option implies a normal level of retinol-binding protein, which does not correlate with the patient's symptoms indicative of vitamin A deficiency.
- **Option D:** This option suggests a very high level of retinol-binding protein, which is not physiologically consistent with the clinical presentation.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that vitamin A deficiency can present with night blindness (difficulty seeing in low light) and that retinol-binding protein levels can be used as an indicator of vitamin A status. Additionally, zinc deficiency can also impair immune function and is related to vitamin A metabolism, as zinc is required for the conversion of retinol to retinal.
## **Correct Answer:** . Decreased