Fanconi Syndrome Leading to Hypophosphatemic Osteomalacia Related to Tenofovir Use

Abstract

Tenofovir disoproxil fumarate (TDF) is used worldwide to treat and prevent Human Immunodeficiency Virus (HIV) infection. Fanconi syndrome is a complication of TDF use and is characterized by inadequate reabsorption of glucose, phosphate and protein in the proximal tubule of the kidney which may eventually lead to osteomalacia manifested by symptoms of pain, muscular weakness and difficulty ambulating. We present a patient with severe osteomalacia due to progressive and unrecognized Fanconi's syndrome, who responded rapidly to TDF withdrawal, oral phosphate repletion and calcitriol. With the widespread use of TDF-containing antiviral regimens, it is critically important that physicians adhere to screening recommendations to detect early Fanconi syndrome, and recognize symptoms of osteomalacia as a serious complication.

Keywords: Fanconi syndrome; HIV; adverse event; hypophosphatemic osteomalacia; tenofovir.

Figure 1

Hip/Femur X-Ray. Patchy regions of sclerosis in the medial subtrochanteric regions, Left (L) >Right (R) corresponding to uptake on bone scan concerning for subacute incomplete fractures. Consistent with Looser’s Zones.

Figure 2

Bone scan of patient showing nonspecific focal uptake in bilateral lesser trochanters, read as compatible with chronic bone remodeling/increased bone turnover. Increased activity in distal R femur, R lateral tibial plateau. Increased activity in R ankle and 1st/3rd metatarsals. Radiotracer activity at L tenth rib.