Abnormal serum concentrations of calcium and fibroblast growth factor 23 (FGF23) are two of a group of interrelated metabolic disturbances—collectively referred to as the chronic kidney disease-mineral bone disorder (CKD-MBD)—that are implicated in the high morbidity and mortality rates in CKD. Here, FGF23 is linked to Marchiafava-Bignami disease.