SLC20A2 and Marchiafava-Bignami disease: Secondary outcomes included plasma biochemistries related to CKD‐MBD and gene expression of the intestinal phosphate transporters, NaPi‐2b/slc34a2, sodium‐dependent phosphate co‐transporter 1 (PiT‐1/slc20a1), and sodium‐dependent phosphate co‐transporter 2 (PiT‐2/slc20a2).