Abstract
Purpose :
To explore histopathological diagnosis and clinical management of microsporidial keratitis in the United States.
Methods :
Retrospective review of medical records for microsporidial keratitis cases with tissue submitted to pathology. Slides were analyzed using a number of special stains and ancillary studies, and the clinical presentation and management was reviewed.
Results :
Our study identified four male patients (35 to 79 years old), none immunosuppressed, with microsporidial keratitis diagnosed through histopathological evaluation following penetrating keratoplasty (PK). In all five specimens, stromal organisms were round to oval, 3-5 microns, uniformly positive on Brown and Hopps (B&H) stain. Stain reactivity varied: Masson Trichrome (MT) in 3/3 cases, Giemsa in 2/2, Gram Weigert in 4/5, Periodic Acid Schiff in 1/3, Acid Fast in 1/4, and Gomori Methanamine Silver in 0/3. Electron microscopy, immunofluorescence and sequencing helped to confirm the diagnosis in some cases. Patient 1 was treated for herpetic keratitis for 10 months, then diagnosed histopathologically after penetrating keratoplasty (PK). He was lost to follow up for a year, and organisms were still present on a repeat PK. Despite treatment with topical fumagillin and oral albendazole, vision remained at hand motion. Patient 2 was treated for over two years for interstitial keratitis of unknown etiology and eventually had a PK. His vision improved to 20/100 following treatment with voriconazole drops. Patient 3 underwent two outside PKs for presumed HSV keratitis. Tissue from the third performed at our hospital showed microsporidial keratitis. Despite treatment with oral albendazole and topical voriconazole, he eventually underwent enucleation. Patient 4 had persistent corneal infiltrates for over 12 months, leading to a PK that revealed microsporidia. Despite treatment with topical voriconazole and intrastromal antifungal injections, his vision remained at hand motion at last follow up.
Conclusions :
This study highlights the challenges in diagnosing corneal microsporidial infections in the US, due to their varied presentations and relative rarity. Histological diagnosis can generally be made based on morphology and a range of special stains, with B&H, MT, and Giemsa being most reliable in our small series. Outcomes are often poor despite appropriate treatment, and more effective therapies are needed.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.