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Tumor-induced osteomalacia

Loida A. Gonzalez-Rodriguez, MD – Assistant Professor, University of Puerto Rico School of Medicine - Endocrinology, Diabetes and Metabolism Division

Anardi A. Agosto Mujica, MD – Endocrinology Fellow, University of Puerto Rico-Medical Science Campus

Margarita Ramirez-Vick, MD – Attending Physician, University of Puerto Rico - Medical Science Campus

Andres J. Ortiz Nieves, MD – Endocrinologist, University of Puerto Rico-Medical Science Campus

Milliette Alvarado-Santiago, MD – Attending Physician, Univeristy of Puerto Rico- Medical Science Campus


Objective :

52 year old male patient presenting with osteomalacia due to phosphate wasting syndrome secondary to a suspected mesenchymal tumor.

Methods : n/a

Results :


Discussion : Case of a 52 year old male patient with past medical history of benign prostatic hyperplasia presenting with progressive symptoms of arthralgia, weakness, and non-fragility fractures. No evidence of leg bowing or short stature in physical examination. Biochemical work-up done due to hypercalcemia symptoms, revealed primary hyperparathyroidism for which parathyroidectomy of the adenoma was performed, and hypophosphatemia. Due to continued polyarthralgias imaging were done (abdominopelvic CT scan, bone scan, and skeletal survey) with evidence of a calcified left lung granuloma, inflammatory changes in both sacroiliac bones, left iliac crest bone lesion with non-diagnostic bone biopsy, left tibial osteochondroma, and left scapular lytic lesion. Bone scan showed progression of costochondral osteogenesis resembling a rachitic rosary, for which diagnosis of osteomalacia was entertained. DXA scan reveled a low BMD (T score at lumbar spine at -2.7 and Z score at -3.2) for which denosumab was prescribed. Due to persistent hypophosphatemia, elevated alkaline phosphatase, low 1,25 vitamin D, and imaging findings, patient was started on calcitriol and phosphate supplementation. He was referred to our endocrinology clinics for suspected osteomalacia. Laboratory values revealed an elevated 24-hour urine collection for phosphorous at 2,317, elevated alkaline phosphatase 433 U/L (30ng/mL), and elevated FGF23 at 1600RU/mL (<180RU/mL). After ruling out secondary causes of renal phosphate wasting and evidence of elevated FGF23, in the setting of multiple site involvement, tumor-induced osteomalacia secondary to a mesenchymal tumor was suspected. FDG-PET and octreotide scintigraphy has been negative at the moment. Phosphate supplementation optimized with clinical improvement.

Conclusion :

Tumor-induced osteomalacia lesions are typically small, benign mesenchymal tumors that may be found in bone or soft tissue, anywhere in the body. Octreotide scintigraphy is successfully used to locate tumors in up to 95% of patients. High-resolution magnetic resonance imaging of the whole body is the currently proposed method of choice to confirm the location of the tumor. Locating the tumor is critical, as complete removal is curative. In 5% of patients the tumors cannot be found; in these cases long-term medical treatment with phosphate supplements and active vitamin D is recommended with active surveillance usually successful. However medical treatment can be cumbersome and associated with complications.

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