Foscarnet Salvage Therapy for Acyclovir-Resistant Varicella Zoster

Abstract

The authors describe an acyclovir-resistant varicella zoster virus infection in a pediatric patient after hematopoietic stem cell transplant, the use of foscarnet as salvage therapy, and review the literature to clarify the pediatric experience with foscarnet in this setting. A novel thymidine kinase mutation is described, along with a new phenotypic assay for characterizing acyclovir resistance in varicella zoster virus.

Herpes Zoster in Autologous Hematopoietic Cell Transplant Recipients in the Era of Acyclovir or Valacyclovir Prophylaxis and Novel Treatment and Maintenance Therapies

“…Although acyclovir-resistant HZ has been described 32 , it is rare in HCT recipients 33,34 , and there was no clinical evidence for resistance in our patients who were taking ACV/VACV prophylaxis at the time of HZ based on subsequent response to these agents. VZV-specific T-cell reconstitution in allogeneic HCT recipients does not appear to be adversely affected by prolonged use of prophylactic ACV after HCT 14 , suggesting that the continued risk for HZ after discontinuation of antiviral prophylaxis likely reflects a prolonged immunodeficiency 9 .…”

Improvement of acyclovir‐resistant herpes zoster infection by amenamevir

“…However, ACV-resistant VZV is a problem for immunocompromised patients that may pose therapeutic dilemmas. 2 Foscarnet and cidofovir are therapeutic options in many of these cases, 3,4 and amenamevir is now another treatment option in Japan.…”

Differences in the Likelihood of Acyclovir Resistance-Associated Mutations in the Thymidine Kinase Genes of Herpes Simplex Virus 1 and Varicella-Zoster Virus

“…It is suggested that the occurrence of viral TK-associating ACVr mutations in VZV is much less frequent than in HSV-1. ACVr VZV is reported rarely in immunocompromised patients (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). In contrast, ACVr HSV-1 occurs in 3.5% to 10% of immunocompromised patients (2,(24)(25)(26)(27)(28).…”