Thrombotic Microangiopathy During Pregnancy: Role of Soluble Fms-like Tyrosine Kinase-1–Placental Growth Factor Ratios

Thrombotic microangiopathies (TMAs) are severe endotheliopathies that can arise in pregnancy and require early recognition. Complement-mediated (C-)TMA should be differentiated from other endotheliopathies of pregnancy because the treatment differs. Here, we report a case of a pregnant woman with acute kidney injury requiring hemodialysis due to C-TMA on the background of a pathogenic C3 variant at 28+5 weeks of gestation. The low soluble Fms-like tyrosine kinase-1 to placental growth factor (sFlt1/PlGF) ratio excluded pre-eclampsia. Eculizumab was started, and therapeutic drug monitoring was applied for optimal dosing. Despite prolonged hemodialysis, fetal well-being was preserved, and delivery was safely postponed till 34+3 weeks of gestation, resulting in a healthy neonate. We also separately report on sFlt1/PlGF ratios measured in a cohort of 11 patients with TMA and coexisting pregnancy. Ten of 11 patients (91%) had low sFlt1/PlGF ratios, excluding pre-eclampsia. Thus, successful pregnancy in women with C-TMA can occur, and sFlt1/PlGF ratios may aid in clarifying the diagnosis and appropriate treatment.