FGF23 can increase the urinary phosphorus excretion rate (FEP = (urinary phosphorus/blood phosphorus)/(urinary creatinine/blood creatinine) × 100 (%)) as a phosphaturic factor and suppress activation of vitamin D, resulting in the major trigger in the course of CKD-MBD (Figure 1) [2]. This evidence concerns the gene FGF23 and Marchiafava-Bignami disease.