Anti-factor H antibody associated hemolytic uremic syndrome following SARS-CoV-2 infection

BACKGROUND: The pathogenesis of autoantibody generation in anti-factor H (FH) antibody associated atypical hemolytic uremic syndrome (aHUS) is unknown and is perhaps triggered by an infectious or environmental agent. We observed an unusual increase of patients with anti-FH antibody associated aHUS coinciding with the second pandemic wave in New Delhi and suspected that SARS-CoV-2 infection might be a potential trigger. METHODS: We screened for SARS-CoV-2 infection using reverse transcriptase polymerase chain reaction (RT-PCR) and serology in 13 consecutive patients with anti-FH antibody associated aHUS during the past year in New Delhi. RESULTS: We report 5 patients, 4–13 years old, who presented with a febrile illness without respiratory symptoms during the second pandemic wave. Of these, 3 patients presented with a relapse 25–85 months following the initial episode of aHUS. SARS-CoV-2 was detected by RT-PCR in 1 patient and by serology in 4 patients (median titer 47.1 cut-off index). Patients had high titers of anti-FH antibodies (median 2,300 AU/ml). Genetic studies, done in 3 of the 5 patients, showed homozygous CFHR1 deletion without other significant genetic abnormalities. Specific management comprised plasma exchanges and oral prednisolone, combined with either cyclophosphamide or mycophenolate mofetil. At median follow-up of 3.3 months, the estimated glomerular filtration rate in 4 patients ranged from 62 to 110 ml/min/1.73 m(2); one patient was dialysis-dependent. CONCLUSION: Increased vigilance is required during the pandemic, especially in patients with anti-FH associated aHUS, who might relapse despite quiescent disease for a prolonged period. GRAPHICAL ABSTRACT: [Figure: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00467-021-05390-4.