We retrospectively analyzed the pharmacokinetic and dynamic parameters of eculizumab in one patient in time, emphasizing various factors which could be taken into account during tapering of treatment.<h4>Case presentation</h4>A nowadays 18-year-old male with a severe, frequently relapsing form of atypical HUS due to a hybrid CFH/CFHR1 gene in combination with the homozygous factor H haplotype, required chronic plasma therapy (PT), including periods with plasma infusion, from the age of onset at 5 months until initiation of eculizumab at the age of 11 years. Here, CFHR1 is linked to hemolytic-uremic syndrome.