Emergencies happen in hematology and oncology. This is a fact. But how do we manage these emergencies? Look no further. In this episode, we talk all about our fourth hematologic emergency: thrombotic thrombocytopenic purpura (TTP).
Thrombotic thrombocytopenic purpura (TTP):
- Be sure to check out episode 009 on thrombocytopenia for a general approach and differential!
- New anemia and thrombocytopenia should raise concerns for TTP!
Workup:
- Peripheral smear - concern for schistocytes. Look at this first! Example of these cells from ASH image bank here
- ADAMTS13 level - always draw ASAP before any intervention
- Repeat CBC
- Reticulocyte count - will have elevated retic count
- Citrated platelet count
- CMP
- PT, PTT, INR
- Fibrinogen
- Haptoglobin
- LDH
- Viral serologies
Clinical manifestations:
- Fever, Anemia, Thrombocytopenia, Renal (AKI), Altered Mental Status
- If you see this - the patient is in bad shape
Mechanism:
- Tiny blood clots form in the body, causing platelet shearing
- Loss of ADAMTS13 - This protein normally is responsible for chopping up von Willebrand’s factor (vWF)
- In the absence of ADAMTS13, vWF multimers are extra long, therefore interacting with platelets/collagen more and causing activation of platelets and clotting system
- This causes red blood cell shearing due to small vessel microthrombi (brain, kidneys, heart)
- Cytokine release causes fevers
Management:
- Do not reflexively transfuse platelets; can make situation worse
- PLASMIC Score: helps to stratify likelihood of TTP; MDCalc link (https://www.mdcalc.com/plasmic-score-ttp)
Treatment:
- Plasma exchange: replacing ADATMS13-deficient plasma with ADAMTS13-rich plasma
- This is different than plasmapheresis, where we replace plasma with albumin
- Steroids: 1mg/kg prednisone daily to stop auto-antibody (against ADAMTS13) production
- Confirm with ADAMTS13 levels; if <10%, this is confirmatory. This is why this is the FIRST step that we just send off as soon as TTP is suspected
- IF YOU DON’T HAVE ACCESS TO PLASMA EXCHANGE: can administer FFP until you can get them to a center than can do plasma exchange
- Caplacizumab: reserved for patients with severe neurological dysfunction, stroke, or myocardial infarction. Check out the NEJM paper on this (below)!
Microangioathic hemolytic anemia (MAHA):
- Umbrella term for red blood cells shearing in the small blood vessels; TTP is one example of a MAHA
References:
https://ashpublications.org/blood/article/129/21/2836/36273/Thrombotic-thrombocytopenic-purpura - great review article from ASH on TTP
https://www.nejm.org/doi/10.1056/NEJMoa1806311 - NEJM paper on caplacizumab
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