Acyclovir-Resistant Herpetic Keratitis: A Case Report.

A clinical case with a high suspicion of acyclovir-resistant herpetic keratitis is described and a review of the mechanisms related to antiviral resistance is performed.

Department of Ophthalmology, Mútua Terrassa University Hospital, Terrassa, Barcelona, Spain.

This is a clinical case of a patient with stromal-predominant herpetic keratitis of more than 10 years of evolution. The patient presented multiple recurrences over the years despite coverage with prophylactic doses of oral valacyclovir. In the last recurrence he presented a reactivation episode of severe stromal keratitis with corneal melting. Suspecting resistance to acyclovir, it was decided to use an intravenous regimen of foscarnet 40mg/kg/8h for 14 days. Due to severe thinning with high risk of corneal perforation, a tectonic keratoplasty with amniotic membrane covering was performed, accompanied by a prophylaxis of valganciclovir 900 mg every 12h, which now been reduced to every 24h.

After discontinuation of treatment and substitution with intravenous foscarnet, no signs of recurrence have been observed. The patient reports a disappearance of ocular pain accompanied by an improvement in corrected visual acuity. In turn, no alterations in renal function, a potential systemic adverse effect of the treatment, are observed.

The case highlights the importance of considering acyclovir resistance in those patients with chronic or recurrent herpetic keratitis, particularly in those with torpid evolution to standard treatments, or with poor response to prophylaxis.

Although we have not performed a viral DNA genetic sequencing test due to the urgency of the clinical picture, this procedure would be the Gold Standard to confirm antiviral resistance.

Resistance to acyclovir is due to genetic mutations that alter the enzymes necessary for viral activity. The most frequent mutation, in 95% of cases, occurs in the thymidine kinase (TK) gene. Secondly, mutations in the DNA polymerase gene (DNA pol).