Haematology, coagulation and transfusion

TTP and thrombotic microangiopathy

Reviewed Nov 2026·3 references
New· views rounded down, updated weekly

Recognise MAHA with thrombocytopenia, use PLASMIC, start urgent plasma exchange and immunosuppression, and distinguish HUS, DIC and pregnancy TMAs.

Definition
TMA = microangiopathic haemolytic anaemia (schistocytes, raised LDH, low haptoglobin, negative DAT) + thrombocytopenia ± organ injury. Immune TTP: ADAMTS13 activity < 10% due to autoantibodies; untreated mortality ~90%.

At the bedside

  1. 1

    Confirm MAHA

    Peripheral smear (schistocytes > 1%), LDH, haptoglobin, reticulocytes, bilirubin, DAT, coagulation (normal in TTP), creatinine, troponin. Send ADAMTS13 before plasma.

  2. 2

    PLASMIC score

    Platelets < 30, haemolysis, no active cancer, no transplant, MCV < 90, INR < 1.5, creatinine < 2 mg/dL: 6-7 = high probability of severe ADAMTS13 deficiency.

  3. 3

    Urgent plasma exchange

    < 4-8 h

    If TTP suspected (PLASMIC high): start TPE (1-1.5 plasma volumes daily) within hours; if TPE delayed, give FFP 15-30 mL/kg meanwhile.

  4. 4

    Immunosuppression

    Methylprednisolone 1 g/day × 3 (or prednisolone 1 mg/kg); rituximab 375 mg/m² weekly; caplacizumab where available.

  5. 5

    Avoid platelets

    Platelet transfusion only for life-threatening bleeding; aspirin/LMWH prophylaxis once platelets > 50 × 10⁹/L.

  6. 6

    Consider differentials

    STEC-HUS (bloody diarrhoea), atypical HUS (complement - eculizumab), DIC, HELLP/pre-eclampsia, malignant hypertension, scleroderma renal crisis, drugs (quinine, gemcitabine, calcineurin inhibitors), infections.

  7. 7

    Monitor response

    Daily platelets and LDH; continue TPE until platelets > 150 × 10⁹/L for 2 days.

Bridge until TPE available

Fresh frozen plasma

IV
Dose
15-30 mL/kg
Worked example
70 kg: 1,050-2,100 mL; watch for volume overload

Immune TTP

Methylprednisolone

IV
Dose
1 g daily for 3 days

Immune TTP

Rituximab

IV
Dose
375 mg/m² weekly × 4
Worked example
BSA 1.8 m²: 675 mg per dose
Open Body surface area (Mosteller)

Immune TTP

Caplacizumab

IV then SC
Dose
10 mg IV before first TPE, then 10 mg SC daily

TMA differential

ConditionClues
Immune TTPVery low platelets (< 30), mild AKI, neuro symptoms, ADAMTS13 < 10%
STEC-HUSBloody diarrhoea, severe AKI
Atypical HUSSevere AKI, complement mutation, ADAMTS13 > 10%
DICProlonged PT/aPTT, low fibrinogen, sepsis/trigger
HELLP / pre-eclampsiaPregnancy > 20 weeks or postpartum, hypertension, raised liver enzymes
Malignant hypertensionVery high BP, retinopathy; improves with BP control
Red flag · call your senior now
Neurological symptoms, chest pain or raised troponin in TTP signal high mortality: urgent TPE and ICU.
Pitfall
Transfusing platelets in TTP: may precipitate thrombosis.
Pitfall
Waiting for ADAMTS13 results (days) before starting plasma exchange.
Pearl
Normal coagulation tests with schistocytes and severe thrombocytopenia point to TTP rather than DIC.

Calculators for this topic

Body surface area (Mosteller)

√(height cm × weight kg ÷ 3600).

References

  1. 1

    Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for treatment of thrombotic thrombocytopenic purpura. J Thromb Haemost 2020;18:2496-502.

  2. 2

    Bendapudi PK, Hurwitz S, Fry A, et al. Derivation and external validation of the PLASMIC score for rapid assessment of adults with thrombotic microangiopathies. Lancet Haematol 2017;4:e157-64.

  3. 3

    Scully M, Cataland SR, Peyvandi F, et al. Caplacizumab treatment for acquired thrombotic thrombocytopenic purpura (HERCULES). N Engl J Med 2019;380:335-46.

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