## **Core Concept**
Capillary leak syndrome is a condition characterized by the leakage of fluid and proteins from the capillaries into the interstitial space, leading to hypotension, edema, and hemoconcentration. This condition can be caused by various factors, including certain medications. The underlying pathophysiology involves increased vascular permeability.

## **Why the Correct Answer is Right**
The correct answer, **Interleukin-2 (IL-2)**, is a cytokine used in immunotherapy for its ability to stimulate the immune system. One of the known side effects of high-dose IL-2 therapy is capillary leak syndrome. This occurs because IL-2 can cause an increase in vascular permeability, leading to the leakage of fluid from the capillaries into the interstitial space.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide a specific drug, making it impossible to assess its relevance to capillary leak syndrome.
- **Option B:** Similarly, this option is blank and cannot be evaluated.
- **Option C:** This option is also blank, lacking specific information about a drug.
- **Option D:** This option is blank as well, providing no details about a drug.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that capillary leak syndrome is a serious side effect associated with certain immunotherapies, notably IL-2. Clinicians must monitor patients on IL-2 therapy closely for signs of capillary leak syndrome, such as hypotension, edema, and decreased urine output.

## **Correct Answer:** . Interleukin-2 (IL-2)