To explore the clinical diagnostic features of Fanconi syndrome (FS) combined with hypophosphatemic osteomalacia (HO) induced by tenofovir dipifurate fumarate (TDF) in a patient with chronic hepatitis B (CHB).

The clinical data of a case of CHB with FS and HO admitted to the Jining No.1 People′s Hospital on May 3, 2022 were reviewed retrospectively, and the literature was reviewed.

The 66-year-old female had a history of more than 20 years of CHB treated with TDF for more than 5 years before she was admitted to hospital due to " recurrent pain of both lower limbs for more than 1 year" . The patient had pain, numbness and discomfort in both lower limbs without obvious inducement 1 year ago, especially in the right lower limb. The pain was more severe, worsened after activity and could be alleviated after rest. Her serum potassium was 3.00 mmol/L, calcium was 2.18 mmol/L, phosphorus was 0.32 mmol/L, and there was no abnomality in blood urea nitrogen and creatinine. Repeated urine tests showed urine glucose ±-2+ , urine protein 0-2+ .The 24-hour total urinary phosphorus was 23.25 mmol. Plain MRI scan of bilateral ankle joints showed multiple bone abnormalities in constituent, tarsal and metatarsal bones of both ankles, and false fracture lines were found. The diagnosis was secondary FS with HO caused by TDF. TDF was discontinued, and antiviral therapy was replaced with tenofovir alafenamide fumarate, vitamin D calcium chewable tablets, vitamin D2 softgel capsules, sodium glycerophosphate, and other medications to correct calcium and phosphorus metabolism disorders, and the patient′s symptoms improved significantly.

Patients with CHB treated with TDF should be aware of the possibility of FS complicating with HO. Clinicians should monitor blood creatinine, blood phosphorus, urine glucose, and urine protein levels both before and during treatment.