Preeclampsia is a multifactorial vascular disease unique to human pregnancy. While genetic and antiangiogenic factors are important contributors to preeclampsia susceptibility, recent studies have shown that dysregulation and/or over-activation of the complement system has an integral role in dis-ease etiology. Furthermore, the role of the coagulation cascade may be underappreciated in the develop-ment of the disease. Traditionally, for research purposes, the pool of preeclampsia cases has been divided into non-severe and severe disease depending on the onset and severity of the symptoms. However, of particular interest are a small but important minority of cases that present with symptoms likening to those of hemolysis, elevated liver enzymes and low platelets syndrome, atypical hemolytic uremic syn-drome, or thrombotic thrombocytopenic purpura, all thrombotic microangiopathy (TMA) diseases, with the hallmark mechanisms of endothelial dysfunction and aberrant activation of complement and coagu-lation cascades. We therefore propose a third class, severe TMA-like preeclampsia to be included in the categorization of preeclampsia patients. Identifying these patients would target research, diagnostic dif-ferentiation, and novel treatment options to the subclass of patients with life-threatening disease that are most likely to benefit from next-generation drug development. (c) 2021 The Authors. Published by Elsevier Inc. on behalf of American Society for Histocompatibility and Immunogenetics. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).