ITP vs TTP
How to tell ITP and TTP apart when a board question makes them look alike.
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Schistocytes with thrombocytopenia identify TTP rather than isolated ITP.
Side by side
Isolated thrombocytopenia with mucocutaneous bleeding and otherwise normal hemolysis markers suggests immune thrombocytopenia.
Thrombocytopenia with microangiopathic hemolytic anemia, neurologic or renal dysfunction, and schistocytes indicates thrombotic thrombocytopenic purpura.
ITP is antibody-mediated platelet destruction and impaired platelet production.
TTP is ADAMTS13 deficiency or inhibition causing ultralarge vWF multimers and platelet-rich microthrombi.
Platelets are low, often below 100,000/uL, with normal PT, PTT, LDH, bilirubin, and peripheral smear lacking schistocytes.
TTP shows thrombocytopenia with schistocytes, elevated LDH, indirect hyperbilirubinemia, low haptoglobin, and normal PT/PTT; ADAMTS13 activity is often below 10%.
The trap
Giving platelet transfusion first in TTP can worsen microthrombosis unless life-threatening hemorrhage is present. Any thrombocytopenia plus MAHA pattern should trigger immediate plasma exchange, not ITP-only therapy.
The repair move
Next best step: start emergent plasma exchange and high-dose glucocorticoids, such as methylprednisolone 1 mg/kg/day or equivalent, while sending ADAMTS13 testing without waiting for results. Add caplacizumab when available and avoid platelet transfusion unless there is critical bleeding.
Try a free question
CoreA 30-year-old woman has new petechiae and gum bleeding. BP 120/74 mm Hg, HR 82/min, temp 36.7 C. Platelets are 22,000/uL, hemoglobin and creatinine are normal, smear shows no schistocytes, and PT/PTT are normal. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Immune thrombocytopenia. Isolated thrombocytopenia with normal hemolysis and coagulation profile is most consistent with ITP.
Why the other choices are tempting
- B. TTP is less likely because schistocytes, hemolysis markers, and neurologic or renal findings are absent.
- C. DIC usually has prolonged coagulation tests and consumptive coagulopathy features.
- D. Aplastic anemia causes pancytopenia rather than isolated severe thrombocytopenia.
- E. HIT requires heparin exposure and usually presents with thrombosis more than mucosal bleeding.
Flashcards
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Which smear finding separates TTP from ITP?
Schistocytes indicate microangiopathic hemolysis and support TTP.
How does coagulation testing usually appear in TTP?
PT and PTT are usually normal in TTP despite severe thrombocytopenia.
Quick answers
What is the fastest way to tell ITP from TTP?
Schistocytes with thrombocytopenia identify TTP rather than isolated ITP.
What is the key clue for ITP?
Isolated thrombocytopenia with mucocutaneous bleeding and otherwise normal hemolysis markers suggests immune thrombocytopenia.
What is the key clue for TTP?
Thrombocytopenia with microangiopathic hemolytic anemia, neurologic or renal dysfunction, and schistocytes indicates thrombotic thrombocytopenic purpura.
What is the common trap with ITP vs TTP?
Giving platelet transfusion first in TTP can worsen microthrombosis unless life-threatening hemorrhage is present. Any thrombocytopenia plus MAHA pattern should trigger immediate plasma exchange, not ITP-only therapy.