Capillary leak syndrome is most likely to develop following the administration of which agent?

• A. cladribine
• B. trans-retinoic acid
• C. interleukin-2
• D. epoetin alpha

Answer: (C)

Capillary leak syndrome happens when cytokines cause the small vessels to become overly permeable, so fluid and proteins move from the bloodstream into interstitial spaces. This leads to edema, low blood pressure, and can affect organ function. The classic setting for this syndrome is high-dose interleukin-2 therapy, used in certain cancers, where IL-2 activates immune cells and drives a surge of inflammatory cytokines like TNF-alpha and IL-1 that loosen endothelial tight junctions. Because of this, patients can develop hypotension and edema during the infusion and require careful monitoring, with treatment focusing on stopping IL-2 and supporting blood pressure and fluids as needed.

Other agents don’t typically produce this capillary leak pattern. Cladribine mainly causes myelosuppression and cytopenias; epoetin alfa can cause hypertension and thrombotic events without the characteristic capillary leakage; trans-retinoic acid can cause a differentiation syndrome with edema and effusions, but the classic capillary leak described in this context is most strongly associated with interleukin-2.