Management and outcome of microsporidia-induced stromal inflammatory keratitis - A long-term follow-up study

To describe the course of disease, management, and outcome of immune stromal keratitis (ISK)/interstitial keratitis (IK) associated with microsporidial epithelial keratitis with a long-term follow-up.

We reviewed the medical records of 20 patients with microsporidia-associated IK between October 2020-2022. Microsporidia involvement was confirmed microbiologically (smear/molecular diagnosis) using corneal epithelium scrapings and clinically characterized by the presence of disciform keratitis, immune ring, and sub-epithelial infiltrates. Patients with over three months of follow-up were included. The course of the disease and management was analyzed.

We found 11 out of 20 (55%) microsporidia-associated IK during the study period followed beyond three months. The mean duration of follow-up was 342.1 ± 178.3 days (100 days-23 months). Topical steroids and topical tacrolimus ointment 0.03% were discontinued in nine out of 11 patients after the resolution of initial episode. Among the five out of nine (45%) had six episodes of recurrences 4 ± 3.9 months after discontinuing medications. Re-scraping was performed in four episodes, and microsporidia spores were detected again on two occasions. Among five patients with recurrence, topical steroids were used in the initial treatment for 6 ± 2.1 weeks, and topical tacrolimus was prescribed to only one patient for eight weeks. For the recurrent attacks, topical tacrolimus was added for over 10 weeks, with topical steroids. The patients were followed up for at least six months, with no new episodes of recurrence.

Microsporidia-associated ISK/IK is a novel condition having a chronic course with recurrences. It requires close follow-up for recurrences at least six months after discontinuing medications, and topical 0.03% tacrolimus ointment is an effective corticosteroid-sparing agent.