New Fellow Bootcamp Series: TTP
An exciting new academic year is about to begin. We know this can be daunting, especially for our newest hematology/oncology fellows. Over the next two weeks, we re-boot some of our high yield episodes you need to know to prepare for your first days as a new fellow and your nights on call.
First up: thrombotic thrombocytopenic purpura (TTP) [Originally episode 018]
Be sure to check out our Rotation Guides to get you in tip-top shape for fellowship!
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
Treatment:
Plasma exchange: replacing ADAMTS13-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!
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
