HUS vs TTP and DIC
How to tell HUS and TTP and DIC apart when a board question makes them look alike.
HUS is diarrhea-kidney MAHA; TTP is neuro MAHA with normal coags; DIC is MAHA plus abnormal coagulation and low fibrinogen.
Side by side
Hemolytic uremic syndrome is MAHA, thrombocytopenia, and acute kidney injury, classically after bloody diarrhea from Shiga-like toxin exposure in a child.
TTP is MAHA plus thrombocytopenia with neurologic findings and normal PT/PTT from ADAMTS13 dysfunction; DIC is systemic coagulation activation with prolonged PT/PTT and low fibrinogen.
Endothelial injury in renal microvasculature creates platelet-rich microthrombi that shear RBCs and injure kidneys.
TTP forms platelet-rich microthrombi from uncleaved large vWF multimers; DIC consumes platelets and clotting factors through widespread thrombin generation.
Schistocytes, elevated LDH, low haptoglobin, thrombocytopenia, and prominent creatinine rise support HUS, often with normal coagulation studies.
Normal PT/PTT with neurologic symptoms supports TTP; prolonged PT/PTT, low fibrinogen, and high D-dimer support DIC.
The trap
Schistocytes can appear in all three, so kidney-vs-neuro emphasis and coagulation studies decide the lane.
Watch it explained
The repair move
When schistocytes show up on a smear with thrombocytopenia, run three diagnostic steps: (1) check PT, PTT, and fibrinogen first (abnormal coagulation studies plus low fibrinogen plus high D-dimer equals DIC; normal coagulation studies points to HUS or TTP); (2) read the organ pattern (a child or adult with bloody diarrhea plus AKI equals typical HUS from Shiga-toxin-producing E coli O157:H7 or Shigella; an adult with neurologic deficits dominating equals TTP from ADAMTS13 deficiency; an adult with AKI without diarrhea equals atypical HUS from complement dysregulation); (3) treat fast (TTP needs urgent plasma exchange plus steroids and is the highest-risk diagnosis if missed; typical HUS gets supportive care and dialysis as needed; atypical HUS responds to eculizumab; DIC needs treatment of the underlying trigger plus supportive transfusion of platelets, FFP, and cryoprecipitate to replace what is being consumed). Never give platelet transfusion in TTP unless life-threatening bleeding because transfused platelets feed the microthrombi.
Try a free question
CoreA child develops bloody diarrhea followed several days later by pallor, thrombocytopenia, schistocytes, elevated creatinine, and normal PT/PTT. Which diagnosis is most likely?
Show answer and explanation
Answer: A. HUS. Post-diarrheal MAHA with thrombocytopenia and acute kidney injury points to HUS.
Why the other choices are tempting
- B. TTP more often emphasizes neurologic findings and ADAMTS13 dysfunction.
- C. DIC should prolong PT/PTT and lower fibrinogen.
- D. ITP causes isolated thrombocytopenia without MAHA or renal injury.
- E. Hemophilia A causes deep tissue bleeding with prolonged PTT, not MAHA.
Flashcards
Tap a card to flip it.
What triad points to HUS?
Microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury point to HUS.
What clue separates TTP from HUS?
Prominent neurologic findings with normal PT/PTT and ADAMTS13 dysfunction point toward TTP.
Quick answers
What is the fastest way to tell HUS from TTP and DIC?
HUS is diarrhea-kidney MAHA; TTP is neuro MAHA with normal coags; DIC is MAHA plus abnormal coagulation and low fibrinogen.
What is the key clue for HUS?
Hemolytic uremic syndrome is MAHA, thrombocytopenia, and acute kidney injury, classically after bloody diarrhea from Shiga-like toxin exposure in a child.
What is the key clue for TTP and DIC?
TTP is MAHA plus thrombocytopenia with neurologic findings and normal PT/PTT from ADAMTS13 dysfunction; DIC is systemic coagulation activation with prolonged PT/PTT and low fibrinogen.
What is the common trap with HUS vs TTP and DIC?
Schistocytes can appear in all three, so kidney-vs-neuro emphasis and coagulation studies decide the lane.