Protein-losing enteropathy as a new phenotype in atypical hemolytic uremic syndrome caused by CD46 gene mutation and recovery from chronic kidney failure by eculizumab treatment

Background: Atypical hemolytic uremic syndrome (aHUS) is a life-threatening thrombotic microangiopathies. Genetic defects in complement alternative pathway have been identified in 60-70% of aHUS individuals. Eculizumab is recommended as first-line therapy. Methods : We collected clinical data of a pediatric aHUS case, who accompanied with protein-losing enteropathy (PLE). Genetic testing was performed. Related literatures of aHUS combined with PLE were reviewed. Results: A 15-year-old Chinese girl was diagnosed with aHUS at 3.7-year- old, and suffered with five episodes, she showed completely resolved with plasma treatment. Severe gastrointestinal symptoms and hypoalbuminemia presented after first episode and protein-losing enteropathy (PLE) was diagnosed. A novel homozygous CD46 variant was identified and FACS showed significantly decreased CD46 expression. She presented a recent relapse with persistent GI symptoms and headache, and progressed to chronic kidney failure, peritoneal dialysis was initiated. Eculizumab was given after 8 months of last recurrence. Surprisingly, PLE was cured, Afterwards, dialysis could be discontinued, eGFR recovered to 44.8ml/min/1.73㎡. Review of literatures indicated PLE with thrombosis was caused by CD55 variants with a mechanism of hyperactivation of complement system. We firstly reported an aHUS case with PLE caused by CD46 variants, both symptoms of PLE and aHUS improved significantly in our case and cases reported with CD55 variants treated with eculizumab, which indicates PLE as a new symptom of aHUS in our case with CD46 variants. Conclusions: Our case expands phenotype of aHUS caused by CD46 mutation, and provide evidence of efficiency of eculizumab after a long chronic kidney failure phase.