We recently identified renalase, a novel flavin adenine dinucleotide (FAD)–dependent oxidase that is secreted into blood by the kidney and is hypothesized to participate in catecholamine metabolism.1,2 Plasma renalase levels are decreased in animals subjected to subtotal nephrectomy (5/6 Nx) and in patients with chronic kidney disease and end‐stage renal disease. This evidence concerns the gene RNLS and chronic kidney disease.