Phosphopenic Osteomalacia with Multiple Fractures as an Adverse Effect of Long-Term Tenofovir Therapy for Hepatitis B

This article presents a case report and a review of sources about hypophosphatemic osteomalacia, a rare adverse effect of chronic hepatitis B treatment with tenofovir disoproxil fumarate. Hypophosphatemic osteomalacia is caused by partial or complete Fanconi syndrome or reduced renal function due to acute or chronic damage to the proximal renal tubules. This case report describes manifestations such as multiple skeletal fractures, including rib and vertebral fractures, left acetabular and sacral fractures, bone and joint pain, signs of neuropathy, and severe muscle weakness. However, bone mineral density remained normal. There was also evidence of osteonecrosis of the talus, scaphoid, and medial cuneiform. Differential diagnoses included vitamin D deficiency, diabetic nephropathy and neuropathy, cancer, and hematologic disorders. The diagnosis was suspected by a decrease in blood phosphate levels and tubular reabsorption of phosphate, and by elevated levels of fibroblast growth factor 23. Discontinuation of tenofovir resulted in rapid clinical improvement and normalization of mineral metabolism, including estimated tubular phosphorus reabsorption and ratio of maximum rate of renal tubular reabsorption of phosphate to glomerular filtration rate.