We report a child with IgAV associated with clinical features of hypertension, nephrotic range proteinuria, acute kidney injury, low serum C3, and normal serum C4, with histopathologic finding on renal biopsy of membranoproliferative glomerulonephritis with C3/IgA co-dominance by immunofluorescence, and extensive characterization of the complement system revealing activation of the alternative pathway, without clear activation of the terminal pathway. The gene discussed is CD79A; the disease is acute kidney injury.