Abstract: Objective To analyze the clinical features of hypophosphatemia osteomalacia induced by adefovir dipivoxil and provide evidence for evaluation of the condition. Methods A retrospective analysis of 21 patients diagnosed as adefovir dipivoxil-induced osteomalacia from January 2012 to January 2019 in the First Medical Center of Chinese PLA General Hospital was conducted to summarize their clinical characteristics. Results The average age of the 21 patients was 53.86±9.98 years,with male to female ratio of 15:6.The time from taking adefovir dipivoxil to onset of bone pain was 2-15 years,with an average of 7.33±3.75 years.The time from symptom onset to diagnosis was 18 (12-30) months.Most patients complained of polyarticular pain or bone pain,and the affected areas included ankles (95.2%),knees (81.0%),rib (71.4%),lumbosacral (66.7%),hip (66.7%),etc.Lower limb weakness developed in 90.5% of patients,and 81.0% of patients had walking difficulty.The conditions could be misdiagnosed as ankylosing spondylitis,osteoporosis,etc.Hypophosphatemia was found in all cases,and 12 cases (57.1%) were in accordance with the diagnosis of Fanconi syndrome.The bone scan showed multiple increased radiopacities in the whole body. Conclusion Long-term use of adefovir dipivoxil may cause hypophosphatemia osteomalacia,most of which manifests with bone pain,arthralgia and osteoporosis.Patients taking adefovir should undergo electrolyte testing and imaging examination regularly to avoid misdiagnosis and mistreatment.