Synopsis
Recognise microangiopathic haemolysis with thrombocytopenia as an emergency, obtain decisive samples without delaying therapy, and separate TTP, STEC-HUS, complement-mediated HUS and secondary thrombotic microangiopathies.
- Thrombotic microangiopathy is a clinicopathological syndrome of small-vessel endothelial injury, microangiopathic haemolytic anaemia, thrombocytopenia and organ ischaemia; it is not a final aetiological diagnosis.
- The laboratory pattern is falling haemoglobin and platelets, schistocytes, raised LDH and indirect bilirubin, reticulocytosis and low haptoglobin. The direct antiglobulin test is usually negative and coagulation may be relatively preserved in TTP.
- Do not wait for the historical pentad of fever, neurological change, renal impairment, anaemia and thrombocytopenia. Many patients have only MAHA and thrombocytopenia when life-saving treatment should start.
Key red flags
Anaemia, thrombocytopenia and fragmented red cells occur with high LDH, low haptoglobin, indirect hyperbilirubinaemia and a marrow reticulocyte response. Severe hypertension and mechanical valves can mimic parts of this pattern.
Investigation priorities
Demonstrate thrombocytopenia and non-immune red-cell fragmentation quickly and trend severity.
Management branches
MAHA and thrombocytopenia have no immediately dominant alternative, especially with cerebral or cardiac features.
- Send citrate plasma for ADAMTS13 activity and inhibitor before any plasma if this causes no delay, plus urgent haemolysis, renal, coagulation, troponin and infection tests.
- Contact the designated regional TTP centre immediately and begin daily plasma exchange, corticosteroid and caplacizumab treatment under its protocol while arranging monitored transfer.
Key medicines
Therapeutic plasma exchangeExchange approximately one to one-and-a-half plasma volumes daily using the regional TTP centre protocol.
CaplacizumabGive 10 mg intravenously before first plasma exchange, then 10 mg subcutaneously after each exchange and daily for 30 days after exchange ends, with specialist extension if needed.