Mechanism:
(1) overproduction of phosphatonins (such as FGF-23, a fibroblast growth factor)
(2) increased levels of phosphatonin result in:
(2a) decreased reabsorption of phosphorus by the renal tubular cells
(2b) downregulation of 1-alpha-hydroxylase in the kidney, resulting in decreased 1,25-dihydroxy vitamin D
(3) the actions of the phosphatonins result in hypophosphatemia
(4) prolonged hypophosphatemia results in osteomalacia
Types of mesenchymal tumors:
(1) mixed connective tissue variant (referred to by Jan deBeur as PMTMCT - phosphaturic mesenchymal tumor, mixed connective tissue type)
(2) osteoblastoma-like
(3) ossifying fibroma-like tumors
(4) nonossifying fibroma-like tumors
Usually these are benign but occasionally malignant variants may occur.
These tumors can be small and hard to locate. Specialized imaging studies have been developed to locate them.
Complete resection of the tumor cause reversal of the syndrome.
