PO26 - Pulmonary Embolism in a case with Thrombotic Thrombocytopenic Purpura after Plasmapheresis

Background: Thrombosis of TTP in microvasculature including small arterioles and capillaries is common and well-described. However, venous thrombosis in TTP confers a unique challenge.

Aims: Herein present a patient with TTP who developed pulmonary embolism (PE) after plasmapheresis.

Methods: Case report

Results: A 46-year-old female with obesity (BMI of 59) visited emergency department for heavy vaginal bleeding for 1 week. Labs were significant for hemoglobin 5.6 g/dL, platelets 26,000 /mcL, and microangiopathic hemolytic anemia (LDH 1221 U/L, indirect bilirubin 0.9 mg/dL, reticulocyte 9.2%, and haptoglobin < 10 mg/dL, 8~10 schistocytes/HPF on peripheral smear). Creatinine 1.14 mg/dL, PT/PTT within normal range. Fibrinogen 490 mg/dL, D-dimer 1252 ng/mL. Direct antiglobulin test, hepatitis, HIV, and pregnancy tests were negative. Bilateral lower extremity doppler was negative for DVT. Plasmic score was 6, so the plasmapheresis and steroids were initiated. ADAMTS 13 later returned less than 2 percent. After plasmapheresis, the platelet count improved to 212,000 /mcL, and the patient was discharged.
The patient returned to the ED the next day for chest pain and shortness of breath. CT angiogram demonstrated right lower segmental/subsegmental PE. Enoxaparin 1mg/kg q12hrs was started. Patient was discharged with enoxaparin for at least 3 months and rituximab was given to reduce recurrence.

Conclusion(s): First, TTP and PE have different mechanisms of thrombosis. TTP produces platelet-rich thrombi in the arterial and capillary microvasculature. The mechanism of PE in this case is explained by TTP itself, large volume plasmapheresis transiently lowering Protein C and S, class III obesity, and immobility.
Second, venous thromboembolism prophylaxis in TTP is crucial. Graduated elastic compression stockings can be utilized at diagnosis and prophylactic enoxaparin is recommended once platelet rises above 50,000/mcL, which is often held due to thrombocytopenia.
Lastly, in patients with Class 3 obesity, weight-based enoxaparin is recommended for DVT prophylaxis and treatment, since clinical data remain limited for DOACs.