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Abstract: FR-PO593

Hypophosphatemia and Phosphate Wasting Due to Oncogenic Osteomalacia in a Patient with Natural Killer T-Cell Lymphoma

Session Information

  • Trainee Case Reports - III
    October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Trainee Case Reports

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Canterbury, John P., Ochsner Clinic Foundation, Jefferson, Louisiana, United States
  • Velez, Juan Carlos Q., Ochsner Clinic Foundation, Jefferson, Louisiana, United States
Introduction

Hypophosphatemia is common electrolyte disorder in hospitalized patients. Urinary phosphate wasting can be caused by oncogenic osteomalacia (OncOsteom), en entity characterized by production of phosphatonins, like fibroblast growth factor 23 (FGF-23). Mesenchymal tumors are the most common cause of OncOsteom and other malignancies are rarely associated. Here we present an unusual case OncOsteom in a patient with Natural Killer T-cell (NKT) lymphoma.

Case Description

A 33 year-old woman was admitted to the hospital with fever, chills, productive cough and myalgias. She had a remote history of mycobacterium avium complex infection and was actively being treated for hepatitis B virus with tenofovir and for hemophagocytic lymphohistiocytosis with etoposide. Upon arrival, the patient was normotensive but in respiratory distress. Examination showed sinus tachycardia and diffuse rales on lung auscultation. Laboratory data revealed serum electrolytes (mEq/L): Na 137, K 3.7, Cl 106, and CO2 23. Others serum chemistries (mg/dL): creatinine 0.4, urea nitrogen 16, calcium 7.7 (serum albumin was 1.6 g/dL, corrected calcium 9.6) and phosphorus 1.5. Intravenous sodium phosphate was aggressively supplemented. Urine phosphate was 63 mg/dL, no glucosuria. Discontinuation of tenofovir did not lead to resolution of hypophosphatemia and the patient continued to require constant IV phosphate replacement for 12 additional days. A diagnosis of OncOsteom was entertained and a FGF-23 level was obtained and found to be elevated at 1940 RU/mL. A 1,25 (OH) vitamin D level was 48 ng/mL and 25 (OH) vitamin D was 8 ng/mL. A bone marrow biopsy was performed and the patient was diagnosed with NKT lymphoma. She continued to deteriorate clinically and expired 1 week later.

Discussion

Hypophosphatemia secondary to OncOsteom is an ominous disorder associated with significant morbidity. It is typically encountered in patients with mesenchymal tumors. Our case is the first reported in a patient with NKT lymphoma. The teaching point is that OncOsteom should be considered in cases of refractory urinary phosphate wasting in the presence of a lymphoproliferative disorder and measurement of FGF-23 level should be considered in those cases to reach a diagnosis.