Oncogenic osteomalacia is a rare
paraneoplastic syndrome characterized by hypophosphatemic
osteomalacia due to renal
phosphate wasting. The same biochemical features are found in patients with
X-linked hypophosphatemic rickets/
osteomalacia and sporadic hypophosphatemic
osteomalacia with unknown etiology.
Oncogenic osteomalacia is cured by resection of the responsible
tumor. In contrast, patients with other types of
hypophosphatemic rickets/
osteomalacia need long-term treatment with large doses of active
vitamin D3. Therefore, detection of the responsible
tumor for
oncogenic osteomalacia has great clinical importance. However, there is no standard method for detecting the
tumor for
oncogenic osteomalacia, and the responsible
tumor is often very difficult to be found. We describe a patient with adult-onset
osteomalacia due to renal
phosphate wasting. Although
oncogenic osteomalacia was suspected, cranial, chest, and abdominal computed tomography scanning, urological and otolaryngological examinations, and detailed palpation for soft tissue mass failed to detect the responsible
tumor. However, magnetic resonance imaging skeletal survey revealed a
tumor in the right femoral bone. Resection of the
tumor resulted in normalization of serum
phosphate and renal
phosphate handling. Because the most frequent causes for
oncogenic osteomalacia are
tumors in bone or soft tissue, magnetic resonance imaging skeletal survey is a very powerful method for detecting the responsible
tumor. Vigorous search for
tumors with this method in patients with hypophosphatemic
osteomalacia would be helpful not only for proper management of patients, but also for clarifying the identity of sporadic hypophosphatemic
osteomalacia.