Physiologically, FGF-23 is mainly expressed in osteoblasts and osteocytes [11], but it may be produced by neoplasms of mesenchymal origin (most commonly phosphaturic mesenchymal tumor mixed connective tissue variant [PMTMCT] or other rare entities including sinonasal hemangiopericytoma, osteosarcoma, hemangioma of bone, etc.)[12]. The gene discussed is FGF23; the disease is neoplasm.