Hyperphosphatemic Familial Tumoral Calcinosis

**Semantic type:** Disease or Syndrome

**Definition:** An autosomal recessive disorder caused by loss-of-function mutation(s) in the GALNT3, FGF23, or KL gene, which encode polypeptide N-acetylgalactosaminyltransferase 3, fibroblast growth factor 23, and klotho, respectively. This condition, the biochemical hallmark of which is hyperphosphatemia caused by increased renal phosphate absorption, is characterized by the progressive deposition of calcium phosphate crystals in periarticular spaces, soft tissues, and/or bone.