Thrombotic Thrombocytopenic Purpura and Other Thrombotic Microangiopathic Hemolytic Anemias

Thrombotic microangiopathies (TMA) are a group of disorders characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and microthrombi leading to ischemic tissue injury. The classification of the TMAs is challenging and constantly evolving with a greater understanding of the molecular basis of the disease. These disorders can be divided into primary or secondary forms. Primary thrombotic microangiopathies occur spontaneously with no associated underlying cause. Secondary forms arise in the context of another disease or trigger, like autoimmune disease, medications, etc. Though rare, thrombotic microangiopathies are life-threatening conditions that require urgent management. Since 2001, ADAMTS13 has been identified as the main factor in the pathogenesis of TTP. Therefore, point-based TTP prediction scores have been validated to predict an acquired ADAMTS13 deficiency. These scores include platelet count, serum creatinine level, and either detectable antinuclear antibodies or D-dimer, reticulocytes, and indirect bilirubin. As these standard investigations are not specific for TTP and may be present in the miscellaneous differential diagnosis for TTP, they should be complemented by analysis of ADAMTS13, the unique marker sensitive and specific for TTP. With prompt therapeutic plasma exchange (TPE) initiation, the average survival rate from the first episode of TTP is 80% to 90%. Long-term follow-up of patients with TTP, including medical consultation, standard biology, and ADAMTS13 activity monitoring, is also justified by the relapsing risk of this disease.