When Immune System and Herpes Virus Infection Collide: A Case of Severe Stromal Herpetic Keratitis in a Patient with Rheumatoid Arthritis Under Methotrexate.

PURPOSE: To report a case of refractory herpes simplex virus keratitis (HSVK) complicated by keratolysis and severe stromal thinning in a patient with rheumatoid arthritis (RA) under treatment with methotrexate (MTX). OBSERVATIONS: A 79‑year‑old patient with a history of HSVK and RA, treated with weekly MTX, presented with pain and photophobia in the right eye. Best‑corrected visual acuity (BCVA) was limited to counting fingers. Slit‑lamp examination revealed a supero-nasal corneal ulcer (area of 2.98 mm2) with deep stromal involvement and keratolysis. A recurrent episode of HSVK was diagnosed, and treatment with 3 times daily oral acyclovir, 4 times daily 0.15% ganciclovir ophthalmic gel, and 3 times daily 0.15% topical dexamethasone was started. After one week, the picture worsened with corneal thinning (corneal thinnest point [CTP] 82 µm) and anterior chamber fibrin. Cycloplegic therapy 3 times daily was added. Considering the refractory course, the history of recurrent HSVK, and the concomitant systemic immunomodulation, the MTX injection scheduled for the subsequent weeks was interrupted. After 2 weeks, conjunctival hyperemia improved (Efron grade II) and a progressive increase of corneal thickness (CTP 199 µm) was documented. Two months later, complete healing was achieved with no signs of active inflammation or recurrence; BCVA improved to 0.4 LogMAR, with mild residual stromal thinning and opacity (CTP 231 µm). CONCLUSION AND IMPORTANCE: This case underscores how systemic immunomodulatory treatment may play a clinically relevant role in patients with recurrent HSVK. In selected cases, a conservative, surgery‑sparing approach through the optimization of systemic therapy can help promoting viral load control and corneal healing.