Changing Epidemiology and Outcomes of Hemolytic Uremic Syndrome in Children: A Prospective National Cohort Study from the Polish Pediatric HUS Registry and the Polish Registry of Renal Replacement Therapy in Children.

Background/Objectives: Hemolytic uremic syndrome (HUS) is a known cause of acute kidney injury in children, but there are few recent reports on its epidemiology and outcome. We aimed to investigate trends in the incidence and the long-term outcomes of both Shiga toxin-producing Escherichia coli -HUS (STEC-HUS) and atypical HUS (aHUS) in Poland over the last 12 years (2012-2023), based on the Polish Pediatric HUS and Pediatric Renal Replacement Therapy (RRT) Registries. Methods: A total of 436 patients (301 with STEC-HUS and 135 with aHUS) were included. Results: The incidence of STEC-HUS increased during the observation period, with a mean of 3.9 cases per million age-related population (marp). The incidence of aHUS was relatively constant with a mean of 1.8/marp. The majority of patients fully recovered, although kidney sequelae were observed at 5-year follow-ups in 31% of children with STEC-HUS, 57% of aHUS subjects in the pre-eculizumab era, and 37% of aHUS subjects who had received eculizumab. The overall mortality rate was 2% for STEC-HUS and 3.7% for aHUS, with no deaths reported in children on eculizumab and mortality mainly attributed to neurological damage. A decreasing incidence of chronic kidney disease stage 5 (CKD5) due to HUS was observed. Conclusions: Despite an unchanging incidence of aHUS and an increasing incidence of STEC-HUS, the kidney outcomes of both diseases have improved significantly over the last 12 years. Mortality from HUS has dropped due to improved symptomatic treatment and the introduction of anti-C5 therapy. The development of CKD5 in childhood as a consequence of HUS has become exceptional.