TTP is a potentially life threatening thrombocytopenia usually caused by inhibition of ADAMTS13 (vWF cleaving protease).
Its classical pentad is present only about 10% of the time:
- Thrombocytopenia
- Microangiopathic haemolysis
- Fever
- Renal injury
- Altered mental status
Mechanism
In the absence of ADAMTS13, ultra large von Willebrand factor causes spontaneous platelet aggregation under conditions of high shear stress, e.g. microvasculature, brain, heart, kidneys. The thrombocytopenia is consumptive due to the thrombosis; the same thrombosis causes the associated MAHA because of the mechanical fragmentation of erythrocytes.
Management
Treatment of ITP is by plasma exchange. This removes the offending antibody (if present) and replaces ADAMTS13. Medications are also used, primarily to suppress antibody production.
- Steroids (prednisone or methylprednisone)
- Rituximab
- Caplacizumab (new kid on the block: an anti-vWF antibody developed by Ablynx NV, a company of which you have probably never heard)