Tumoral calcinosis - An unusual etiology

Tumoral calemosis (TC) is a disorder of enhanced renal tubular phosphate reabsorption resulting in hyperphosphatemia and ectopic calcifications. Gene analyses have confirmed that destabilizing mutations within fibroblast growth factor-23 (FGF23) and Ga1NAc transferase-3 (GALNT3) are responsible for heritable TC. Herein, we present a patient with phenotypic and biochemical features of TC, whose evaluation revealed no mutations in either the FGF23 or GALNT3 genes and normal circulating C-terminal and intact FGF23 concentrations. The patient is a 12-year-old African American man with ectopic, subcutaneous mineral deposits, with a diagnosis of tumoral calcinosis based on collective clinical features. Plasma FGF23 concentrations were determined using both an assay that measures full-length FGF23 and one that recognizes the C-terminal portion. Gene analysis was performed on DNA isolated from peripheral WBCs. The patient's calcium and PTH concentrations were normal. Serum phosphorus concentrations ranged 5 to 6.7 mg/dL. 1,25-Hydroxy vitamin D levels were elevated. FGF23 C-terminal fragment concentrations were 53.79 RU/mL (reference interval 55 +/- 50 RU/mL) and intact FGF23 concentrations were 11 pg/mL (reference interval 28 +/- 2.2 pg/mL). Gene analysis showed no mutations in either FGF23 or GALNT3 genes.