In 3 patients (18.8%), the FGF-23 secreting tumor was not operable or not localized by commonly employed nor advanced techniques of nuclear medicine imaging (indicated as NL); in 7 patients (43.7%), TIO recurred 6 months after first surgical treatment (indicated as R); and in 6 patients (37.5%) the disease was persistent after specific treatment (i.e., persistent hypophosphatemia or hypophosphatemia recurrence within 6 months after treatment, as specified above, indicated as P). The gene discussed is FGF23; the disease is hypophosphatemia.