A Case of Postpartum Atypical Hemolytic Uremic Syndrome Caused by CORIN Gene Mutation

Introduction: Atypical hemolytic uremic syndrome (aHUS) is a rare disease, characteristics of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, often associated with dysfunction of the alternative pathway of complement. AHUS with CORIN gene mutation have not been described in adult patients. Case Description: A 31-year-old Female patient was presented with severe preeclampsia at 34 weeks of gestation history. A lower segment cesarean section was performed on March 11, 2025. After the operation two days, the patient developed thrombocytopenia and oliguria, hemolytic Anemia, liver dysfunction. The renal biopsy revealed thrombotic microangiopathy (TMA) and Acute tubular injury (ATI)(Figure). The Concentration of Complement Factor H (CFH), Complement Factor I (CFI), Anti-C3 Convertase Antibody, Anti-Human Complement Factor H Antibody and Anti-ADAMTS13 Antibodies were normal. ADAMTS13 Activity is also normal. Clinical picture fit with aHUS as diagnosis. Treatment with plasma exchange, Glucocorticoids, Hemodialysis, Fresh Frozen Plasma were started before admission, but the kidney function was not complete recovery. Treatment with complement inhibitor -Eculizumab was started and patient gradually recovered. Whole exome sequencing identified heterozygous variants in the CORIN in this patient. Discussion: CORIN is a serine protease primarily expressed in cardiomyocytes, responsible for activating atrial natriuretic peptide (ANP) and regulating fluid balance, blood pressure, and renal sodium excretion. Variants in the CORIN gene can lead to reduced or absent function, resulting in impaired ANP activation, which may contribute to pregnancy-related kidney injuries such as preeclampsia and acute kidney injury during pregnancy. Eculizumab is a monoclonal antibody targeting complement protein C5, primarily used to treat complement-mediated disorders such as: Paroxysmal nocturnal hemoglobinuria (PNH), Atypical hemolytic uremic syndrome (aHUS) HELLP syndrome. Corin deficiency-induced kidney injury is primarily associated with ANP deficiency, rather than excessive complement activation. Successful treatment of aHUS with eculizumab in a patient with CORIN gene mutation has not been previously reported.