Тumor-induced Hypophosphatemic Rickets – Three Cases
Author: Vlahov Y.1, Borisova A-M.1, Fukumoto S.2, Shimizu Y.3,Ivanova R.4, Zahariev T.5
Ohridski University of Sofia, Bulgaria;
Abstracts:
Rickets / Osteomalacia are frequent disturbances in Ca-P metabolism, distinguishing between hypocalcemic and hypophosphatemic osteomalacia. The most common is hypocalcemic osteomalacia, which is associated with vitamin D deficiency mainly due to lifestyle. The hypophosphatemic type of osteomalacia is hereditary or tumor-induced (TIO) and is associated with reduced reabsorption of phosphate (P) in the proximal renal tubules and resistance to the effects of vitamin D. Chronic hypophosphatemia leads to rickets / osteomalacia. The gene for FGF23 was discovered in 2000, and on this basis, several types of hypophosphatemic rickets with high serum levels of FGF23 have been identified. Most often, congenital hypophosphatemic osteomalacia is due to an X-linked mutation (XLH) of the PHEX gene (phosphate-regulating gene with homologies to endopeptidases on the X chromosome), i.e. the phosphate regulating gene with homology to endopeptidases on the X chromosome. X-linked hypophosphatemia and tumor-induced osteomalacia are the most common causes of hypophosphatemic vitamin D resistant rickets/osteomalacia.
Clinical cases: For a period of 25 years (1997-2023), 12 patients with hypophosphatemic rickets were diagnosed and followed up. Out of a total of 12 patients in the whole group, Tumor-induced osteomalacia (TIO) was suspected in half, and localization of the primary tumor was actively sought for years in each patient. Three cases of men with TIO will be presented, in two of which a FGF23 overproducing tumor was located and successful surgical treatment was performed. In the following years, the patients have a normal calcium-phosphorus metabolism and are clinically healthy. These are the first cases in Bulgaria successfully treated for this rare disease.
