FGF23 and Marchiafava-Bignami disease: CKD-MBD encompasses metabolic bone disease, vascular calcifications, as well as changes in blood biochemistry such as secondary hyperparathyroidism, hyperphosphatemia, lowered levels of the vitamin D hormone 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], chronic metabolic acidosis, elevated circulating Wnt (Wingless/integrated-1) inhibitors, and increased concentrations of intact fibroblast growth factor-23 (FGF23) (1, 2).