Anti-factor H autoantibody-associated hemolytic uremic syndrome in an Argentine pediatric cohort

Aim: To describe the clinical characteristics and frequency of anti-factor H (FH) autoantibody-associated atypical hemolytic uremic syndrome (aHUS) in the first cohort of Argentine patients. Methods: The presence of anti-FH autoantibodies in 70 pediatric patients with suspected aHUS was investigated between 2013 and 2022. Clinical and laboratory parameters were collected and compared between patients who were positive and negative for anti-FH antibodies. Results: The 70 patients screened for anti-FH autoantibodies presented clinical features of non-immune microangiopathic hemolytic anemia, thrombocytopenia and renal injury. Positive titers were found in 14 children [mean: 1,938 arbitrary units per mL (AU/mL), range 179–8,500]. Due to missing clinical data, two patients who tested positive for anti-FH and 20 patients who tested negative for anti-FH were excluded from the data analysis. The laboratory features and clinical manifestations of anti-FH-positive aHUS cases (n = 12) were very similar to those of subjects with no autoantibodies detected (n = 36). Treatment administration was heterogeneous among the 12 patients analyzed. Dialysis was performed in six patients in total. Five children received plasmapheresis, while three patients were treated with plasma exchange followed by administration of eculizumab. Two patients received eculizumab only and one showed significant improvement solely through supportive care. Eight patients in total received immunosuppressive therapy. Follow-up of three patients showed a significant decrease of anti-FH autoantibody titers in 2/3 after treatment and during clinical remission. Conclusions: The cohort of 70 pediatric patients in this study demonstrated that the frequency of anti-FH autoantibody-associated aHUS in Argentina is 20%. The implementation of anti-FH testing in the country can potentially contribute to improved treatment and follow-up for patients with autoimmune aHUS.