Uncommon Presentation of Atypical Hemolytic Uremic Syndrome: A Case Report

Atypical hemolytic uremic syndrome (aHUS) is an ultra-rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and renal damage. Its presentation as nephrotic syndrome (NS) during first year of life is uncommon; we describe a child with clinical and laboratory findings of NS whose renal biopsy revealed thrombotic microangiopathy (TMA). A previously healthy 4-month-old male was admitted with severe dehydration, diarrhea and anuria. Laboratory results showed electrolyte disturbances, increased serum creatinine, anemia without schistocytes, thrombocytosis, normal lactic dehydrogenase (LDH) levels, hypoalbuminemia hypercholesterolemia and decreased C3 levels. After rehydration hematuria and massive proteinuria were also documented and an initial diagnosis of NS of the first year was established. Studies seeking for infectious agents were negative. During hospitalization he continued to be oligo-anuric needing dialysis and a renal biopsy was performed, which showed TMA findings. We here considered the diagnosis of aHUS and started plasma infusions as a bridge until starting eculizumab. After two infusions urine output improved leading to discontinuation dialysis. The diagnoses of STEC infection and thrombocytopenic thrombotic purpura were ruled out. Factor B, H, I and properdin levels were normal. Antibodies against CFH negative were negative. Screening for genes causative of aHUS detected a heterozygous variant in CFHR3 of uncertain significance. On day 20, treatment was switched to eculizumab, which induced a progressive remission of the NS. This case outlines the need for a heightened diagnosis suspicion of this already rare disease since early initiation of eculizumab therapy improves its prognosis.