False-positive magnetic resonance imaging skeletal survey in a patient with sporadic hypophosphatemic osteomalacia

Oncogenic osteomalacia (OOM) is a rare disease characterized by renal phosphate wasting and osteomalacia [1]. More than 100 patients, have been reported to have rickets and/or osteomalacia induced by various types of tumors [2]. As clinical symptoms associated with hypophosphatemia or osteomalacia improved or completely disappeared on removal of the tumors, an unknown phosphaturic factor was believed to play an important role in the development of OOM [3-6]. Detection of the responsible tumor has great importance; however, there has been no standard method. Magnetic resonance (MR) imaging is reported to be a useful method for the diagnosis of bone and soft tissue tumors. Many groups successfully discover the lesion of the responsible tumor by MR imaging [7-10]. Especially, MR imaging was the only technique to point out the responsible tumor in some cases because plain roentgenograms and X-ray computed tomography (CT) did not contribute to finding the tumors [7,8]. After successful removal of these tumors, the biochemical abnormalities such as hypophosphatemia were normalized, indicating that the tumors were responsible for the disease. We describe herein a case of false-positive MR imaging of a responsible tumor inducing osteomalacia, and discuss the limitations of diagnosis by MR imaging.