Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2016) 41 GP40 | DOI: 10.1530/endoabs.41.GP40

ECE2016 Guided Posters Bone & Calcium Homeostasis (10 abstracts)

Severe osteomalacia caused by a phosphaturic mesenchymal tumor secreting fibroblast growth factor 23: a case report

Lisa Ravarani 1 , Michael Faust 1 , Alexander Quaas 4 , Marc Bludau 2 , Matthias Schmidt 3 , Inka Allendorf 1 , Tengü Topuzoglu-Müller 1 , Ruth Hanßen 1 , Oliver Schary 5 & Jens C Brüning 1

1Poliklinik für Endokrinologie, Diabetologie und Präventivmedizin. Uniklinik Köln, Köln, Germany; 2Klinik und Poliklinik für Allgemein-, Vizeral- und Tumorchirurgie. Uniklinik Köln, Köln, Germany; 3Klinik und Poliklinik für Nuklearmedizin. Uniklinik Köln, Köln, Germany; 4Institut für Pathologie. Uniklinik Köln, Köln, Germany; 5Klinik II für Innere Medizin; Nephrologie, Rheumatologie, Diabetologie und allgemeine Innere Medizin. Uniklinik Köln, Köln, Germany.

Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic syndrome clinically presenting with recurring fractures, muscular weakness and pain. Laboratory values of affected patients are characterized by renal phosphate wasting and hypophosphatemia caused by an overexpression of fibroblast growth factor 23 (FGF- 23), a hormone belonging to the group of phosphatonins regulating phosphate and vitamin D homeostasis. Pathologically, it is secreted especially by small (and thus difficult to locate) mesenchymal tumors, leading to a significant delay from onset of (often debilitating) symptoms to diagnosis. TIO was first described in 1947 and so far only approximately 300 cases have been reported in the literature.

We present the case of a 41-year old female patient with a 4-year history of recurring fractures of the metatarsal bones and growing muscle pain of the extremities leading to a markedly decreased physical activity. The detailed workup showed reproducible low levels of serum phosphate and 1,25-OH Vitamin D and an increased fractional excretion of urine phosphate. FGF-23 was increased 20-fold (Ref.: 110 kRU/l, measured value 2100 kRU/l). In the subsequently performed imaging diagnostics (ultrasound, DOTATATE-PET-CT) a 2×2×1 cm tumor was located on the left pubic bone. The patient underwent surgery and in the histopathological work-up a benign mesenchymal tumor was confirmed. After complete excision, the serum and urine phosphate normalized rapidly, FGF-23 levels were tested 2 weeks after surgery and had decreased to normal (35 kRU/l). Accordingly, the patient’s symptoms greatly improved shortly after surgery and completely resolved over the course of 6 months. So far, there is no sign of tumor recurrence during a 6-month period of follow-up.

Our aim of presenting this case report is to increase awareness that any patient with hypophosphatemia, unexplained recurrent fractures and muscle weakness should undergo workup for TIO as this remains an extremely rare but potentially curable disease.

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