title: Corneal microsporidiosis. Report of case, including electron microscopic observations.
abstract: OBJECTIVE
  To report a case of corneal stromal infection caused by a protozoon of the genus MICROSPORIDIA:, including clinical, histopathologic, and electron microscopic observations.
  
  
  METHODS
  Case report.
  
  
  METHODS
  Light and electron microscopy studies were performed on keratectomy specimens from a 67-year-old immunocompetent man who had a unilateral chronic stromal keratitis that was refractory to medical treatment. Initial corneal biopsy followed by lamellar and penetrating keratoplasty were performed on the patient. All the specimens were studied histopathologically.
  
  
  RESULTS
  Light microscopy of the corneal biopsy and the subsequent keratectomy specimens demonstrated myriad small, round to oval microsporidial organisms measuring 3.5 to 5.0 micrometer in length that stained positively with the periodic acid-Schiff, Grocott-methenamine silver, and acid-fast methods and were gram positive. Electron microscopic observations demonstrated viable blastospores that had a thin osmiophilic outer cell wall and contained 11 to 13 coils of the filament. The light and electron microscopic features, the tinctorial characteristics, and the selective corneal stromal involvement are consistent with microsporidial keratitis.
  
  
  CONCLUSIONS
  Microsporidiosis should be considered in the differential diagnosis of a culture-negative stromal keratitis refractory to medical treatment. The diagnosis can be easily established based on the morphologic features of the protozoa in the keratectomy specimens. No effective medical treatment for the stromal disease is available. Full-thickness keratoplasty is suggested because, in our patient, lamellar keratoplasty did not preclude recurrence of the disease.
authors.affiliation: Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. rfont@bcm.tmc.edu
authors.forename: R L
authors.initials: RL
authors.lastname: Font
authors.forename: A N
authors.initials: AN
authors.lastname: Samaha
authors.forename: M J
authors.initials: MJ
authors.lastname: Keener
authors.forename: P
authors.initials: P
authors.lastname: Chevez-Barrios
authors.forename: J D
authors.initials: JD
authors.lastname: Goosey
mesh_terms: D000368:Aged; D000818:Animals; D001706:Biopsy; D003319:Corneal Stroma / Q000469:parasitology* / Q000648:ultrastructure; D003937:Diagnosis, Differential; D015822:Eye Infections, Parasitic / Q000469:parasitology* / Q000473:pathology; D006801:Humans; D007634:Keratitis / Q000469:parasitology* / Q000473:pathology; D015948:Keratoplasty, Penetrating; D008297:Male; D008854:Microscopy, Electron; D016816:Microsporida / Q000302:isolation & purification* / Q000648:ultrastructure; D016881:Microsporidiosis / Q000469:parasitology* / Q000473:pathology