Microsporidial Stromal Keratitis: Clinical Features, Unique Diagnostic Criteria, and Treatment Outcomes in a Large Case Series

PURPOSE:To describe the history, clinical features, and outcomes of a large case series of microsporidial stromal keratitis with emphasis on probable predictors of the etiology in this rare and unspecified form of keratitis. METHODS:Retrospective analysis of cases seen between January, 2002, and December, 2013, diagnosed at LV Prasad Eye Institute as having microsporidial stromal keratitis based on clinical, microbiology, and histopathology examination. Outcomes of medical and surgical management with visual recovery were documented. RESULTS:There were 34 cases of microsporidial stromal keratitis with a mean age of 43.3 years (range 2–77 years) and male preponderance. The duration of symptoms was chronic in most cases (mean duration of 288 days). Nearly half of the cases had a history of trauma, in the age group of 20 to 50 years. The most common clinical misdiagnosis was herpes simplex virus keratitis (26.5%) followed by fungal keratitis (17.6%). This could be attributed to the nonspecific clinical picture of diffuse multifocal stromal lesions in 82.4% of cases. The organisms were detected in microbiological evaluation of corneal scrapings in 47% cases, and histopathological detection of the organisms showed a positivity rate of 92.3%. Surgical management was necessary in the majority of the cases (73.5% of patients). CONCLUSIONS:The typical history of trauma with a smoldering, diffuse form of keratitis refractory to conventional medical therapy, responding to surgical removal for recovery is clearly demonstrated as a recurring feature in the majority of the cases. Patients presenting with this characteristic clinical picture should be suspected to harbor this rare pathogen, and early surgical interventions should be considered.