Abstract 15: Tumor Induced Osteomalacia Case Series – A Tertiary Care Centre Experience

Background: Tumor-induced osteomalacia is a rare, acquired paraneoplastic syndrome, including hypophosphatemia, high serum alkaline phosphatase, reduced active vitamin D, suboptimal bone mineral density, bone pain, fragility fractures, and muscle weakness. Case Description: We present 6 patients who had hypophosphatemia and were diagnosed to have TIO [Table 1].{Table 1} Discussion: In our case series, male: female ratio is 2:1. Mean age of the group was 39 years. Most of the patients were in forties and fifties (67%). One was a child. All patients had proximal myopathy of long duration at presentation. Mean duration of symptoms present were 4.1 years. The child had clinical and X-ray features suggestive of rickets. Other patients presented with fragility fractures. All patients had hypophosphatemia with a mean phosphorus of 1.24 mg/dl. All patients had low Tubular Maximum Reabsorption of Phosphate in relation to glomerular filtration rate (TMP/GFR) suggestive of renal phosphate wasting. FGF-23 wasnot done in all patients due to affordability issues. All patients underwent functional imaging (Ga-68DOTATATE PET) first followed by anatomical imaging (MRI/CT). Ga-68 DOTATATE scan revealed lesion in all patients. Lesions were located in Lower limbs (50%), head and neck region (33%) and in upper limb (16%). 4 patients underwent surgical excision of the lesions [Table 1]. 3rd patient had malignant TIO with metastatic lesions in the right lung and hypophosphatemia persisted despite surgical excision and subsequently underwent peptide receptor targeted radionuclide therapy (PRRT) with Lutetium following which hypophosphatemia improved. Patient remained asymptomatic for 6 years despite the poor survival rate associated with malignant TIO. Follow up scan of that patient after 8 years showed new lesions in lungs and he was initiated on Chemotherapy. Fourth patient was a known case of Hemophilia B, whose symptoms improved with phosphorus supplementation and in view of the surgical risk, surgery was deferred. 6th patient underwent bone curettage with grafting. But there was incomplete removal and she is currently on phosphate supplements. Other 3 patients were completely cured and is under follow up. Conclusion: Although, Tumour induced Osteomalacia is a rare disease, we had 6 patients in 5 years. Serum phosphorus is a freely available investigation and can be used as a simple screening method for all patients with nonhealing fractures, bone pain and proximal muscle weakness. In the evaluation of TIO, functionalimaging, if possible, should be done first. If any lesion detected in imaging, surgical excision is mandatory. If lesion not localised or surgery not amenable, medical management modalities including PRRT should be consideredespecially in cases of malignant TIO along with phosphorus supplementation.