ITP vs TTP
How to tell ITP and TTP apart when a board question makes them look alike.
ITP is isolated platelets; TTP is thrombocytopenia plus MAHA and organ injury, even without the full pentad.
Side by side
Isolated thrombocytopenia with mucocutaneous bleeding and otherwise normal coagulation studies.
Thrombocytopenia with MAHA, schistocytes, renal or neurologic findings; fever may occur but the full pentad is uncommon.
Autoimmune platelet destruction, often after infection or immune trigger.
ADAMTS13 deficiency or inhibition causes platelet-rich microthrombi.
Low platelets with normal RBC morphology supports ITP.
Schistocytes, high LDH, and normal PT/PTT support TTP; plasma exchange is the urgent treatment move.
The trap
Petechiae and mucosal bleeding can occur in both; the smear and organ findings separate them.
Watch it explained
The repair move
If platelets are low, scan the smear; thrombocytopenia plus MAHA is enough to treat TTP urgently with plasma exchange.
Try a free question
CoreA child develops petechiae after a viral illness. Platelets are low, hemoglobin is normal, smear shows no schistocytes, and PT/PTT are normal. Which diagnosis is most likely?
Show answer and explanation
Answer: A. ITP. Isolated thrombocytopenia after a viral trigger points to ITP.
Why the other choices are tempting
- B. TTP has thrombocytopenia plus MAHA and organ injury.
- C. DIC has abnormal coagulation tests and low fibrinogen.
- D. Hemophilia causes deep bleeding with prolonged PTT, not isolated thrombocytopenia.
- E. HUS causes MAHA, thrombocytopenia, and renal injury.
Flashcards
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What smear finding turns isolated thrombocytopenia into TTP?
Schistocytes show microangiopathic hemolysis, which moves the answer away from simple platelet destruction.
Why are PT and PTT usually normal in TTP?
The problem is platelet microthrombi from ADAMTS13 failure, not broad consumption of clotting factors.
Quick answers
What is the fastest way to tell ITP from TTP?
ITP is isolated platelets; TTP is thrombocytopenia plus MAHA and organ injury, even without the full pentad.
What is the key clue for ITP?
Isolated thrombocytopenia with mucocutaneous bleeding and otherwise normal coagulation studies.
What is the key clue for TTP?
Thrombocytopenia with MAHA, schistocytes, renal or neurologic findings; fever may occur but the full pentad is uncommon.
What is the common trap with ITP vs TTP?
Petechiae and mucosal bleeding can occur in both; the smear and organ findings separate them.