Pediatric thrombotic thrombocytopenic purpura

Child‐onset thrombotic thrombocytopenic purpura ( TTP ) is a rare entity of thrombotic microangiopathy ( TMA ). The pathophysiology of the disease is based on a severe functional deficiency of ADAMTS 13 (activity <10%), the specific von Willebrand factor ( VWF )‐cleavage protease. This deficiency may be either acquired (associated anti‐ ADAMTS 13 autoantibodies) or congenital (resulting from biallelic mutations of ADAMTS 13 gene). ADAMTS 13 deficiency is responsible for the accumulation of high molecular weight multimers of VWF and the formation of platelet thrombi in the microcirculation. Consequently, microangiopathic hemolytic anemia and consumption thrombocytopenia are associated with organ ischemia. The differential diagnosis with other TMA s, autoimmune cytopenias or hematological malignancies may be challenging. The exploration of ADAMTS 13 (activity, antibodies, antigen, ADAMTS 13 gene) supports the diagnosis of TTP . The first‐line treatment of the acute phase of TTP is based on plasmatherapy. In congenital TTP , patients with a chronic disease benefit from a prophylactic plasmatherapy. In autoimmune TTP , steroids and B‐cells depleting therapies increasingly are used together with plasma exchange. Long‐term follow‐up including the monitoring of ADAMTS 13 activity is mandatory. A severe decrease in ADAMTS 13 activity (<10%) may predict relapses and preemptive B‐cell depletion with rituximab can be used to prevent relapses.