Background: There are limited data on infants with atypical hemolytic uremic syndrome (aHUS). The aim of this study was to determine the clinical and laboratory features, and to evaluate treatment modalities and outcomes in infants with aHUS. Materials and Methods: Relevant data on patients with onset of aHUS at age <2 years were obtained from the Turkish Pediatric aHUS Registry. Results: Among the 146 patients included in the Registry, 53 (36%) (23 male and 30 female) were enrolled for the study. Age at disease onset was ≤1 year in 29 of the patients. In all, 21 (40%) of the patients developed neurological symptoms. Disease-causing mutations were noted in 14 (36%) of the 39 patients in which genetic analysis was performed. Plasma therapy was performed in 42 (79%) patients; eculizumab therapy was administered to treat the first episode of aHUS in 33 (62%) patients and in 5 patients as the first- line therapy. In total, 38 (72%) patients received renal replacement therapy (RRT), 3 (6%) died due to acute illness, and 4 (8%) were discharged from hospital with RRT. Follow-up visit data were available for 46 patients and the median duration was 23 months (range 3–129 months). End-stage renal disease developed only in 1 patient. Proteinuria and hypertension persisted in 17 (37%) and 20 patients (44%) respectively. Eculizumab treatment was continued in 25 of the 39 patients during the follow-up period. Conclusion: One-third of the aHUS patients had disease onset during infancy. The prognosis of this life-threatening disease seems to get better with improved treatment modalities.

Keywords:
Atypical hemolytic uremic syndrome, Children, Plasma therapy, Eculizumab, Treatment, Outcome
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