Severe Hypophosphatemia Potentially Associated with Intracellular Phosphate Shift Concomitant with Acute Kidney Injury in a Patient with Rapidly Proliferating Diffuse Large B-cell Lymphoma

An 85-year-old woman with diffuse large B-cell lymphoma developed severe hypophosphatemia (serum phosphate 0.3 mg/dL) concomitant with acute kidney injury (serum creatinine 2.05 mg/dL) following chemotherapy. Because urine phosphate was undetectable, hypophosphatemia was likely due to the vigorous uptake of phosphate into the rapidly proliferating tumor cells, also known as tumor genesis syndrome (TGS), and acute kidney injury was potentially attributed to the antibiotics sulfamethoxazole/trimethoprim. Oral phosphate supplementation and antibiotic discontinuation alleviated both the abnormalities. This case was unusual, as tumorigenesis syndrome is seldom seen in patients with lymphoma, and acute kidney injury usually leads to hyperphosphatemia. The present case emphasizes the importance of vigilance in hypophosphatemia due to TGS during chemotherapy.