Immune Thrombocytopenic Purpura vs Thrombotic Thrombocytopenic Purpura (TTP) / Hemolytic Uremic Syndrome
Immune Thrombocytopenic Purpura and Thrombotic Thrombocytopenic Purpura (TTP) / Hemolytic Uremic Syndrome are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Immune Thrombocytopenic Purpura vs Thrombotic Thrombocytopenic Purpura (TTP) / Hemolytic Uremic Syndrome at a glance
- Immune Thrombocytopenic Purpura: Isolated thrombocytopenia from autoantibody-mediated platelet destruction with normal-to-increased marrow megakaryocytes.
- Thrombotic Thrombocytopenic Purpura (TTP) / Hemolytic Uremic Syndrome: Thrombotic microangiopathies — TTP from ADAMTS13 deficiency, HUS classically from Shiga toxin; both produce microangiopathic hemolysis with thrombocytopenia.
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Side-by-side comparison
| Feature | Immune Thrombocytopenic Purpura | Thrombotic Thrombocytopenic Purpura (TTP) / Hemolytic Uremic Syndrome |
|---|---|---|
| At a glance | Isolated thrombocytopenia from autoantibody-mediated platelet destruction with normal-to-increased marrow megakaryocytes. | Thrombotic microangiopathies — TTP from ADAMTS13 deficiency, HUS classically from Shiga toxin; both produce microangiopathic hemolysis with thrombocytopenia. |
| Classic presentation | Isolated thrombocytopenia with petechiae and wet purpura in an otherwise well child 1-3 weeks after a viral illness, or in a young adult woman.; Mucocutaneous bleeding: petechiae, ecchymoses, epistaxis, gingival bleeding, menorrhagia; Hematuria, GI bleeding less common; Intracranial hemorrhage rare but most feared (~1% in adults); Often… | Microangiopathic hemolytic anemia + thrombocytopenia + schistocytes on smear + normal coagulation studies — assume TTP/HUS until proven otherwise.; Classic TTP pentad (rarely all 5; even 2 of 5 in correct context warrants treatment): microangiopathic hemolytic anemia, thrombocytopenia, neurologic symptoms (confusion, headache, focal… |
| Workup / key labs | Isolated thrombocytopenia (<100,000/μL) with otherwise normal CBC and smear, and exclusion of secondary causes. Diagnosis of exclusion.; CBC — isolated thrombocytopenia; Hb and WBC normal (unless bleeding-related anemia); Peripheral smear — large platelets (immature, recently released); RULE OUT schistocytes (TTP/HUS/DIC), blasts… | Microangiopathic hemolytic anemia + thrombocytopenia + schistocytes ± end-organ dysfunction. TTP confirmed by ADAMTS13 activity <10%; STEC-HUS by positive stool studies; aHUS by exclusion + complement workup.; CBC — anemia, thrombocytopenia (often <50K in TTP, <100K in HUS); Peripheral smear — schistocytes (helmet cells, fragmented… |
| Imaging | Not routinely indicated; imaging directed at suspected secondary cause | Head CT/MRI if neurologic symptoms (exclude hemorrhage before plasma exchange line placement); Renal ultrasound if persistent AKI |
| First-line treatment | Observation alone for platelets >30,000/μL without bleeding (adults) — most authoritative guidelines (ASH 2019); Glucocorticoids — first-line for platelets <30K or bleeding: prednisone 1 mg/kg/day OR dexamethasone 40 mg/day × 4 days (high-dose dexamethasone often preferred for faster response and shorter course); IVIG 1 g/kg × 1-2 days… | TTP (acquired): EMERGENCY plasma exchange (PLEX) — initiate as soon as TTP suspected; do not wait for ADAMTS13 result. Replaces deficient ADAMTS13 and removes autoantibody. Daily until platelet count >150K for ≥2 days; TTP: high-dose glucocorticoids (methylprednisolone 1 g IV × 3 days or prednisone 1 mg/kg) to suppress autoantibody;… |
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