Bone scintigraphic patterns in patients of tumor induced osteomalacia

Abstract

Tumor induced osteomalacia (TIO) or oncogenic osteomalacia is a rare condition associated with small tumor that secretes one of the phosphaturic hormones, i.e., fibroblast growth factor 23, resulting in abnormal phosphate metabolism. Patients may present with non-specific symptoms leading to delay in the diagnosis. Extensive skeletal involvement is frequently seen due to delay in the diagnosis and treatment. The small sized tumor and unexpected location make the identification of tumor difficult even after diagnosis of osteogenic osteomalacia. The bone scan done for the skeletal involvement may show the presence of metabolic features and the scan findings are a sensitive indicator of metabolic bone disorders. We present the bone scan findings in three patients diagnosed to have TIO.

Keywords: Bone scan; fibroblast growth factor 23; hypophosphatemia; tumor induced osteomalacia.

Figure 1

Technetium 99m methylene diphosphonate whole body bone scan showing increased radiotracer uptake over the mandible, ribs, vertebrae and sternum suggestive of metabolic bone disease. Prominent costochondral beadings and increased tracer uptake over multiple growth plates are also noted

Figure 2

Whole body bone scan showing increased uptake in left proximal fibula (focal), bilateral multiple ribs, bilateral shoulder, acetabulum and femoral heads and mildly increased focal uptake in right mid foot

Figure 3

Whole body bone scan shows increased tracer uptake in bilateral maxillary bones, bilateral shoulder, wrist, sternoclavicular, knee and ankle joints, multiple ribs and mid shaft of bilateral femora (pseudofractures)