Aims To report the clinical manifestations, ultrastructure and evaluate the efficacy of therapeutic lamellar keratectomy (TLK) and penetrating keratoplasty (PK) for microsporidial stromal keratitis (MSK).
Methods Fourteen MSK cases between 2009 and 2018 were recruited. Each patient’s clinical presentation, light microscopy, histopathology, PCR and electron microscopy (EM) of corneal samples were reviewed.
Results The patients were 70.0±4.7 years old (average follow-up, 4.5 years). Time from symptoms to presentation was 10.6±13.0 weeks. The corneal manifestations were highly variable. Corneal scrapings revealed Gram stain positivity in 12 cases (85.7%) and modified Ziehl-Neelsen stain positivity in 9 (64.3%). Histopathology revealed spores in all specimens, while sequencing of small subunit rRNA-based PCR products identified Vittaforma corneae in 82% of patients. EM demonstrated various forms of microsporidial sporoplasm in corneal keratocytes. All patients were treated with topical antimicrobial agents or combined with oral antiparasitic medications for >3 weeks. As all patients were refractory to medical therapy, they ultimately underwent surgical intervention (TLK in 7, PK in 6 and 1 received TLK first, followed by PK). Postoperatively, the infection was resolved in 78.6% of the patients. Nevertheless, a high recurrence rate (21.4%) was noted during 3-year follow-up, with only two patients retained a final visual acuity ≥20/100.
Conclusion MSK usually presents with a non-specific corneal infiltration refractory to antimicrobial therapy. The diagnosis relies on light microscopic examinations on corneal scrapings and histopathological analyses. Surgical intervention is warranted by limiting the infection; however, it was associated with an overall poor outcome.
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J-HH and S-HT contributed equally.
H-YH and C-LW contributed equally.
Contributors JHH and SHT designed the study. HYH and JHH prepared the manuscript. All authors (HYH, CLW, SHL, WCL, FCH, JHH, SHT) collected the clinical data. HYH, SHL and JHH carried out the statistical analysis and analysed the data. SHT supervised the research. All authors (HYH, CLW, SHL, WCL, FCH, JHH, SHT) reviewed and revised the manuscript.
Funding This study was funded by National Cheng Kung University Hospital (grant: NCKUH-10802016 to J.H. Hung).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study was approved by the Institutional Review Board of National Cheng Kung University Hospital (A-ER-107–101) and was conducted in accordance with the tenets of the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
Author note Hsin-Yu Huang and Cheng-Lin Wu contributed equally to this study and should both be regarded as first authors. Jia-Horung Hung and Sung-Huei Tseng contributed equally to this study and should both be regarded as co-corresponding authors.