Hyperphosphatemic familial tumoral calcinosis (HFTC; MIM 211900) is an autosomal recessive metabolic disorder characterized by the progressive deposition of calcium phosphate crystals in periarticular spaces, soft tissues, and also bone. Patients with HFTC may also have angioid streaks of the retina, vascular calcifications, painful swellings of the long bones, periosteal reaction, cortical hyperostosis, and skin changes similar to pseudoxanthoma elasticum (PXE; MIM 264800). Hyperphosphatemia, which reaults in tumoral calcinosis is caused by increased renal absorption of phosphate due to loss-of-function mutations in the FGF23 or GALNT3 gene. One homozygous mutation has been reported in the KL gene in a patient with HFTC. FGF23 mutations can also cause hypophosphatemic rickets, autosomal dominant (ADHR; MIM 193100).