Tumor-induced osteomalacia: a case of diagnostic dilemma.
Tumor-induced osteomalacia is typically caused by benign mesenchymal tumors of vascular or skeletal origin. Overexpression of fibroblast growth factor 23 (FGF-23) by these tumors is associated with decreased resorption of phosphate in the renal tubules. This phosphate wasting leads to the characteristic findings of hypophosphatemia and hyperphosphaturia. Chronic hypophosphatemia causes abnormal mineralization of bone, increased alkaline phosphatase and, in the longer term, osteomalacia. Localization and resection of the FGF-23-secreting tumor offers the best chance of cure. We report a case of a 74-year-old woman diagnosed with numerous fractures on bone scintigraphy. Bone biopsy confirmed osteomalacia. Biochemical investigations showed hypophosphatemia, hyperphosphaturia, and increased alkaline phosphatase, suggesting the presence of an FGF-23-secreting tumor. Biochemistry also showed hyperparathyroidism and subclinical hyperthyroidism. Thyroid and parathyroid scintigraphy were performed and showed separate areas of focally increased tracer uptake in the neck. The patient underwent octreotide scintigraphy to localize an alternative site of tumor. This showed focally increased tracer uptake in the neck and in the abdomen. The patient underwent a hemithyroidectomy, parathyroidectomy, and adrenalectomy. Histopathology showed a papillary carcinoma of the thyroid, a parathyroid adenoma, and an adrenal adenoma. Postoperatively the patient showed rapid symptomatic and biochemical improvement.
Robertson
Andrew
A
Department of Nuclear Medicine, Concord Hospital, Concord, NSW 2139, Australia.
Mansberg
Robert
R
Mansberg
Victor
V
Van der Wall
Hans
H
Hooper
Michael
M
D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D000089703:Fibroblast Growth Factor-23; D050723:Fractures, Bone / Q000175:diagnosis* / Q000209:etiology; D005598:Fractures, Spontaneous / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D009378:Neoplasms, Multiple Primary / Q000150:complications* / Q000175:diagnosis*; D015282:Octreotide; D010018:Osteomalacia / Q000175:diagnosis* / Q000209:etiology*; D019275:Radiopharmaceuticals; D051598:Whole Body Imaging
C000717427:FGF23 protein, human; D019275:Radiopharmaceuticals; D000089703:Fibroblast Growth Factor-23; D015282:Octreotide