FGF-23 transmitted tumor – induced hypophosphatemic osteomalacia: A rare case of a young woman with recurrent fractures and review of the literature

Abstract

Highlights Tumor-transmitted osteomalacia is a rare FGF 23 transmitted phosphaturic disease. Delay of diagnosis is common due to small and clinically silent underlying tumors. The most sensitive imaging modality is 68 Ga-DOTA-TOC-PET/CT-scan. Complete resection of the tumor mass cures this paraneoplastic disease.

Unusual Presentation and Surgical Treatment of a Phosphaturic Mesenchymal Tumor in a Knee

“…An estimated 500 cases of TIO with typical small tumor producing FGF23 and causing hypophosphatemia in adults have been reported ( 4 ). Patients with TIO always complain of progressive musculoskeletal pain and muscle weakness with fractures caused by bone insufficiency.…”

“…The first step in locating the responsible foci is to collect a complete medical history and conduct a thorough physical examination. Next, imaging examinations should be carried out: functional imaging is the initial step, followed by anatomical imaging ( 4 ). More recently, somatostatin receptor (SSTR) analogues conjugated to positron-emitting isotopes such as 68 Ga have become available and can be used to locate the PMTs.…”

“…The innovation in our treatment plan of TIO was to place a static polymethylmethacrylate (PMMA) spacer in the tumor patient to wait until the conditions were suitable for a tumor-type knee prosthesis, which has not previously been done. Once the tumor causing TIO has been located and successfully removed, the typical biochemical abnormalities of this condition are reversed and patients’ symptoms start to improve within days or weeks after surgery, but the bone healing may take up to a year or more ( 4 ). When the tumor cannot be located or completely resected, other medical treatment is necessary which mainly involves the use of phosphate supplements and 1,25(OH) 2 D. When surgery with wide margins cannot be performed, adjuvant radiotherapy is recommended to avoid recurrence, but it is still controversial and has limited use ( 1 ).…”

“…Due to the nonspecific symptoms and difficulty in locating tumors, the diagnosis of TIO is often elusive. And according to statistics, latency to diagnosis is 4 years by median and can take up to 22 years ( 4 ). When TIO is suspected, and if the patient’s condition permits, phosphate, creatinine, and calcium levels in serum and urine should be measured, as well as serum PTH, 1,25(OH) 2 D, FGF23, total or alkaline phosphatase, proteins (by electrophoresis).…”

A Case of Low Phosphorus Osteomalacia in a Young Woman

“…Secondary Hypophosphorous osteomalacia is mostly caused by tumor. Tumor related Hypophosphorous osteomalacia (TIO) is caused by the excessive production of FGF-23 in tumor [5,6], acting on proximal renal tubules, inhibiting phosphate reabsorption and hydroxylation of 25 hydroxyvitamin D, resulting in a series of clinical changes.…”