Overactivation of Complement Alternative Pathway in Postpartum Atypical Hemolytic Uremic Syndrome Patients with Renal Involvement

Problem Postpartum atypical hemolytic uremic syndrome (a HUS ) is a life‐threatening syndrome with unclear pathogenesis. The current study aimed to investigate the clinical and pathological features, complement activation status, and the genetic variations in a C hinese cohort of patients with renal biopsy‐proven postpartum a HUS . Method of study Five patients with postpartum a HUS were recruited. Renal biopsy specimens were examined and scored. Plasma levels of complements were detected, and coding sequences of complement regulators were screened. Anti‐ CFH / CFI autoantibodies were further detected. Results Patients with postpartum a HUS patients presented with severe clinical manifestations and renal involvement. The renal biopsies of the five patients showed typical features of thrombotic microangiopathies. The levels of the following complement components, C 4d, B b, C 3a, C 5a, and SC 5b‐9, were significantly elevated in patients with postpartum a HUS compared with normal non‐pregnant controls. The plasma levels of CFH and CFI significantly decreased in patients with postpartum a HUS compared with normal pregnant women. Three CFH single nucleotide polymorphisms ( SNP s) were identified in the five patients. Two patients presented with CFH autoantibodies. Conclusion Postpartum a HUS is a clinical syndrome with severe renal damage. Genetic deficiencies and autoantibodies of CFH may lead to alternative pathway overactivation and participated in the pathogenesis of postpartum a HUS .