STEC-triggered DEAP-HUS in a toddler: successful management with eculizumab and mycophenolate mofetil without...

Deficiency of CFHR proteins and autoantibody-positive HUS (DEAP-HUS) is a rare autoimmune subtype of atypical HUS that is distinct from typical Shiga toxin-producing Escherichia coli (STEC)-associated HUS. We report the case of a 30-month-old child initially presenting with STEC-associated HUS whose severe clinical course prompted complement investigation despite confirmed STEC positivity. Markedly elevated anti-factor H antibody titers and a homozygous CFHR1-CFHR3 deletion led to reclassification as DEAP-HUS. The patient was treated with eculizumab without high-dose corticosteroids, followed by mycophenolate mofetil (MMF) introduced at month 5, allowing successful discontinuation of complement blockade at month 9. Anti-factor H antibody titers remained stable throughout follow-up without clinical relapse, suggesting that MMF monotherapy provides sufficient immunological stabilization even in the absence of significant antibody reduction.