In a neonate with a large vascular lesion and thrombocytopenia, what is the mechanism behind the low platelet count?

• A. Sequestration of platelets within the vascular lesion
• B. Consumption due to widespread DIC
• C. Decreased platelet production in bone marrow
• D. Immune destruction by antibodies

Answer: (A)

Kasabach-Merritt phenomenon: platelets are trapped and consumed inside the abnormal vascular lesion, so the tumor acts as a reservoir that sequesters platelets and drives local intravascular coagulation. This sequestration leads to thrombocytopenia and often coagulopathy. It's not about reduced platelet production in the bone marrow, nor immune destruction, and while a systemic coagulopathy can accompany it, the driving mechanism is the platelet trapping within the tumor.