Nakano et al. recently reported that the serum intact FGF23 level is the earliest indicator among various CKD-MBD-related factors and that a high intact FGF23 level and a low 25-hydroxyvitamin D (25D) level independently predict poor renal outcomes, even after adjusting for other MBD-related factors, in patients with pre-dialysis CKD [58]. Here, FGF23 is linked to Marchiafava-Bignami disease.