Fanconi Syndrome Associated with Long-term Adefovir and Subsequent Tenofovir Therapy for Chronic Hepatitis B Infection

Adefovir dipivoxil (ADV) and tenofovir disoproxil fumarate (TDF) are nucleotide analogues used to treat chronic hepatitis B (CHB) infection. Nephrotoxicity associated with the use of these medications causes Fanconi syndrome, a rare condition involving generalized dysfunction of the proximal renal tubule causing impaired reabsorption of glucose, uric acid, and phosphate. Fanconi syndrome has been previously reported in patients with human immunodeficiency virus (HIV) or HIV-CHB coinfection treated with other antiretroviral therapies. However, it is rarely reported in patients with CHB monoinfection. We observed a case of Fanconi syndrome in a 61-year-old woman with CHB monoinfection and a history of long-term ADV therapy (42 months), followed by TDF treatment for 9 months. She presented with ankle pain and a tingling sensation in both lower extremities. Laboratory tests revealed hypokalemia, hypocalcemia, hypophosphatemia, hypouricemia, proteinuria, and glycosuria. This case illustrates the importance of recognizing Fanconi syndrome associated with nucleotide analogue treatment and the need to carefully observe symptoms and monitor renal function in these patients. (Korean J Med 2016;91:174-178)