aHUS associated with C3 gene mutation: a case with numerous relapses and favorable 20-year outcome.

Background: Atypical hemolytic uremic syndrome (aHUS) is frequently associated with gene mutations in complement-regulatory proteins and activators. Different complement C3 gene mutations have been associated with different outcomes in aHUS.

Case-diagnosis/treatment: We report the case of a 21-year-old male with a C3 heterozygous gene mutation (p.Ile1157Thr) who developed aHUS at the age of 10 months and had six relapses, the last at the age of 14.5 years. Each relapse was characterized by an apparent predominance of hematological manifestations with milder renal involvement and was followed by complete recovery, with creatinine values and hematological parameters usually recovering after the 3rd to 6th day of hospitalization. The patient was treated with plasma infusion, apart from the initial and the last episode, when dialysis was needed. Twenty years after the onset, he retains normal renal function, with no proteinuria or hypertension. One similar case of highly recurrent aHUS carrying the same C3 mutation as our patient with recovery of renal function has been previously reported.

Conclusions: We further support that aHUS associated with the p.Ile1157Thr C3 mutation may be highly recurrent, but with recovered renal function. The prevalent p.Ile1157Thr C3 gene mutation has variable disease manifestations and both severe and milder renal phenotypes have been found.