Histological changes throughout treatment. Bone biopsies stained with Toluidine Blue dramatic reduction in osteoid thickness following phosphorus supplementation. (A) Bone biopsy in 2015 with large amounts of osteoid tissue. (B) Bone biopsy in 2016 after optimized 25(OH)-vitamin D and Calcium supplementation with no improvement. (C) Bone biopsy in 2017 after phosphorus supplementation showing the mineralization of osteoid tissue.