Haematology for MRCP Part 2

A 41-year-old woman presents with confusion, fever and petechiae. Haemoglobin 78 g/L, platelets 12 × 10⁹/L, creatinine 138 micromol/L. Blood film shows numerous schistocytes. PT and APTT are normal, fibrinogen is normal. ADAMTS13 activity is less than 5%. What is the most appropriate immediate treatment?

1. Urgent plasma exchange correct Correct. This is thrombotic thrombocytopenic purpura, confirmed by severely deficient ADAMTS13. Plasma exchange replaces the deficient enzyme and removes the inhibitory antibody, and it transformed mortality from around 90% to under 20%. It is started on clinical suspicion, not on the assay result.
2. Platelet transfusion to correct the thrombocytopenia Wrong, and traditionally regarded as harmful. Transfused platelets fuel further microvascular thrombosis. Reserve for life-threatening haemorrhage.
3. Eculizumab Wrong here. Complement inhibition is the treatment for atypical haemolytic uraemic syndrome, where ADAMTS13 activity is NOT severely reduced and renal impairment dominates.
4. Broad-spectrum antibiotics and supportive care Wrong as the primary treatment. Sepsis is a differential, but normal coagulation with schistocytes and profound ADAMTS13 deficiency identifies TTP, and delay is measured in lives.
5. Fresh frozen plasma infusion alone A holding measure only if exchange is genuinely unavailable. Infusion supplies ADAMTS13 but cannot remove the autoantibody and is volume-limited.

The point: Microangiopathic haemolysis with thrombocytopenia and NORMAL coagulation screen separates TTP and HUS from DIC. ADAMTS13 below 10% means TTP: plasma exchange, steroids, and caplacizumab in many centres. No platelets unless the patient is bleeding to death.

Source: BSH guideline on the diagnosis and management of thrombotic thrombocytopenic purpura British Society for Haematology · tier 2, specialty society or college