Case Report of Development of Atypical Hemolytic-Uremic Syndrome in Pregnancy

Atypical hemolytic-uremic syndrome (aHUS) is an ultra-rare (orphan) disease with a progressive course, which is a systemic thrombotic microangiopathy resulting from uncontrolled activation of the alternative complement pathway. There exist the so called ‘obstetric' thombotic microangiopathies (pre-eclampsia, HELLP syndrome) which are considered as triggers causing development of aHUS in pregnancy in genetically predisposed female patients. Here, the main peculiarity of these pathologies is the improvement of the condition of the puerpera after delivery. In case of ‘non-obstetric' thombotic microangiopathies, delivery does not lead to regress of symptoms, on the contrary, microangiopathic process progresses with rapid development of multiorgan failure. The development of thrombotic thrombocytopenic purpura and aHUS in pregnancy may induce physiological changes in the organism of a pregnant woman. There occurs a build-up of the activity of von Willebrand factor with a parallel reduction of the activity of ADAMTS 13 enzyme (metalloprotease that cleaves its super-large multimers). This is probably a physiological adaptation of the body to minimize blood loss during childbirth. As a result of the imbalance, the risk of developing thrombotic microangiopathy increases by the end of II — beginning of III trimester. The concept of chronic uncontrolled activation of the alternative complement pathway implies a genetic defect of regulatory proteins with increased formation of C5 convertase, increased release of C5a — a strong chemoattractant, and of membrane–attacking complex C5b–C9, which leads to damage to endothelial cells, exposure of the subendothelial layer and thrombosis. The currently used drug eculizumab is a recombinant humanized monoclonal antibody that binds to the complement C5 protein and suppresses the activation of complement-mediated cell lysis. The article presents a clinical case of the development of aHUS in a patient during pregnancy, the main stages of diagnostic search are considered, routing is determined and the therapy used is justified.