Autoimmune encephalitis following varicella-zoster virus infection after hemodialysis for acyclovir-induced nephrotoxicity and neurotoxicity

Abstract Background Valacyclovir (VACV), a drug for the treatment of herpes zoster, is a prodrug of acyclovir (ACV). ACV is known to have a low protein binding rate and is well removed by dialysis, with good clinical outcomes. However, to the best of our knowledge, there have been no reports of patients with ACV encephalopathy who developed a consciousness disorder again after improvement of impaired consciousness after hemodialysis. Alterations in consciousness due to autoimmune encephalitis may occur within a few months after herpesvirus treatment. Post-infectious autoimmune encephalitis has recently been recognized. In this report, the case of a patient treated with a standard dose of VACV who was found to have impaired consciousness and renal dysfunction after its administration is described. Case presentation The case of a 74-year-old Japanese woman with ACV-induced acute kidney injury (AKI) and encephalopathy followed by post-infectious autoimmune encephalitis is presented. She was prescribed VACV at the standard dose and analgesics for varicella-zoster virus infection. A few days later, she was admitted to our hospital with acute disturbance of consciousness and AKI. The serum creatinine value before and after admission was 0.81 mg/dL and 5.58 mg/dL, respectively. ACV-induced nephrotoxicity and encephalopathy were suspected because her symptoms improved rapidly after hemodialysis. Extremely elevated concentrations of ACV in the blood and cerebrospinal fluid in the early period of her hospital admission were discovered later. Furthermore, somnolence and cognitive dysfunction occurred 1 month after infection without renal dysfunction, and it was thought that post-infectious autoimmune encephalitis may have developed. She was treated by steroid pulse therapy. Her consciousness and memory impairment recovered again. Although anti- N -methyl- d -aspartate receptor (NMDAR) antibodies were negative, autoimmune encephalitis can also develop due to immune reactions other than anti-NMDAR antibodies. Conclusions Although hemodialysis has been established as a treatment for ACV nephropathy and encephalopathy, there have been no reports of recurrence of consciousness disorder or development of autoimmune encephalitis afterward. Sufficient care should be taken even after discharge, and if a consciousness disorder recurs, clinical examination and lumbar puncture, keeping in mind autoimmune encephalitis, should be performed, and a systematic management strategy should be implemented.