Atypical HUS Associated with CFH/CFHR-1 Hybrid Gene

Atypical hemolytic uremic syndrome is a rare form of thrombotic microangiopathy caused by complement pathogenic variants. We describe a case of a 33-year-old woman who presented as rapidly progressing renal failure requiring dialysis and had anemia, microhematuria, low C3, normal C4 levels, and normal platelet count. Renal biopsy revealed arteriolar thrombotic microangiopathy and acute tubular injury. Patient was treated with plasma exchange and hemodialysis as required. This resulted in partial recovery at 1 month. Genetic workup by multiplex ligation-dependent probe amplification revealed a 1.5 times higher signal intensity on downstream region of CFH gene and 50% reduced intensity of exon 6 of CFHR1 gene, suggesting a gene conversion event, similar to those previously reported from Spain and Portugal.