Life-Threatening Extrarenal Manifestations in an Infant with Atypical Hemolytic Uremic Syndrome Caused by a Complement 3-Gene Mutation

Background: Atypical hemolytic uremic syndrome (aHUS) is a rare, life-threatening disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment caused by uncontrolled activation of the complement system. About 20% of patients show extrarenal manifestations, with central nervous system involvement being the most frequent. We described the clinical course and management of aHUS in an infant, that was caused by a complement 3 (C3) gene mutation with severe extrarenal manifestations. Case Presentation: A 4-month-old girl visited our hospital for jaundice and petechiae. Laboratory tests revealed microangiopathic hemolytic anemia, thrombocytopenia, and hyperazotemia. She was diagnosed with aHUS with a C3 p.E1160K mutation. Daily fresh-frozen plasma (FFP) therapy was administered; however, she experienced the severe extrarenal manifestations of pulmonary hemorrhage and gastrointestinal bleeding. With aggressive treatment, supportive care, and daily FFP transfusion, the patient recovered and was discharged after 72 days of hospital stay, on a regular FFP transfusion. Four months after diagnosis, she was switched to eculizumab treatment. Twenty months have passed since then and she has been relapse-free until now. Conclusion: aHUS is rare but has a devastating course if not properly treated. Severe extrarenal manifestations, such as pulmonary hemorrhage and gastrointestinal bleeding, can develop in aHUS caused by a C3 mutation. In our case, long-term management with eculizumab resulted in relapse-free survival.