A 76-year-old woman is brought to the emergency department due to left leg pain. Seven days after undergoing bilateral total knee arthroplasty. Current medications include simvastatin, aspirin, and low molecular weight heparin. His vital signs are within normal limits. The surgical incision over her knees is healing well. Her left posterior calf is tender and swollen to the knee. Examination of the skin shows multiple coalescing blisters with areas of necrosis. Laboratory studies show a platelet count of 32,000/mm3. Which of the following is the most likely cause of this patient's thrombocytopenia?

Question

A 76-year-old woman is brought to the emergency department due to left leg pain. Seven days after undergoing bilateral total knee arthroplasty. Current medications include simvastatin, aspirin, and low molecular weight heparin. His vital signs are within normal limits. The surgical incision over her knees is healing well.  Her left posterior calf is tender and swollen to the knee. Examination of the skin shows multiple coalescing blisters with areas of necrosis. Laboratory studies show a platelet count of 32,000/mm3.   Which of the following is the most likely cause of this patient's thrombocytopenia?

Quizplus · Accepted Answer

Eductional Objective: Heparin-induced thrombocytopenia type 2 results from the formation of IgG antibodies to complexes of heparin and endogenous platelet factor 4.  The major manifestation is thrombocytopenia, which typically occurs 5-10 days after heparin initiation due to the destruction of antibody-coated platelets by splenic macrophages.  Widespread intravascular platelet activation also results in a high risk of arterial and venous thrombosis.

A 76-Year-Old Woman Is Brought to the Emergency Department Due