Oncogenic osteomalacia
| Oncogenic osteomalacia | |
|---|---|
| Other names | Tumor-induced osteomalacia |
Oncogenic osteomalacia, also known as oncogenic hypophosphatemic osteomalacia, is an uncommon disorder resulting in increased renal phosphate excretion, hypophosphatemia and osteomalacia. It may be caused by a phosphaturic mesenchymal tumor.
Signs and symptoms
Adult patients may present with worsening musculoskeletal symptoms, muscle weakness,[1] myalgias, bone pains and fatigue which are followed by recurrent fractures. Children present with difficulty in walking, stunted growth and deformities of the skeleton (features of rickets).[2] There can also be a significant delay between the beginning of symptoms to diagnosis, which research reflects as being between 2.5 and 28 years.[3][1]
Cause
Tumor-induced osteomalacia is usually referred to as a
A phosphaturic mesenchymal tumor is an extremely rare
Pathogenesis
FGF23 (
Diagnosis
Biochemical studies reveal hypophosphatemia (low blood phosphate), elevated alkaline phosphatase and low serum 1,25 dihydroxyvitamin D levels. Routine laboratory tests may not include serum phosphate levels and this can result in considerable delay in diagnosis. Even when low phosphate is measured, its significance is often overlooked. The next most appropriate test is measurement of urine phosphate levels. If there is inappropriately high urine phosphate (phosphaturia) in the setting of low serum phosphate (hypophosphatemia), there should be a high suspicion for tumor-induced osteomalacia. FGF23 (see below) can be measured to confirm the diagnosis but this test is not widely available.
Once hypophosphatemia and phosphaturia have been identified, begin a search for the causative tumor, which may be small and difficult to detect. Gallium-68 DOTA-Octreotate (DOTA-TATE) positron emission tomography (PET) scanning is the best way to locate these tumors.[10] If this scan is not available, other options include Indium-111 Octreotide (Octreoscan) SPECT/CT, whole body CT or MRI imaging.
Differential diagnosis
Serum chemistries are identical in tumor-induced osteomalacia,
Treatment
If the tumor cannot be located, begin treatment with calcitriol (1–3 µg/day) and phosphate supplementation (1–4 g/day in divided doses). Tumors that express somatostatin receptors may respond to treatment with octreotide. If hypophosphatemia persists despite calcitriol and phosphate supplementation, administration of cinacalcet has been shown to be useful.[11]
References
Further reading
- Chong WH, Molinolo AA, Chen CC, Collins MT (June 2011). "Tumor-induced osteomalacia". Endocrine-Related Cancer. 18 (3): R53–R77. PMID 21490240.
- Wasserman JK, Purgina B, Lai CK, Gravel D, Mahaffey A, Bell D, Chiosea SI (September 2016). "Phosphaturic Mesenchymal Tumor Involving the Head and Neck: A Report of Five Cases with FGFR1 Fluorescence In Situ Hybridization Analysis". Head and Neck Pathology. 10 (3): 279–285. PMID 26759148.