Abstract
A 71-year-old woman with previously undiagnosed human T-lymphotropic virus type 1 (HTLV-1) infection presented with fever, urinary difficulties, acute abdominal pain, and severe acute kidney injury (AKI). Diagnostic evaluations confirmed acute pyelonephritis (APN) and acute focal bacterial nephritis (AFBN). Despite antibiotic treatment, she required temporary hemodialysis and eventually developed chronic kidney disease. This case highlights the importance of considering APN and AFBN as differential diagnoses in patients presenting with acute abdominal pain and severe AKI. It also underscores the need to investigate predisposing conditions. Notably, neuropathic bladder can be an isolated neurogenic manifestation of chronic HTLV-1 infection. Therefore, a thorough assessment of urinary dysfunction is essential in patients with APN and chronic HTLV-1 infection.