Microsporidia is an underdiagnosed cause of keratoconjuctivitis
March 29 2018
Microsporidia are closely related to fungi. They form spores. They cause keratoconjunctivitis and stromal keratitis. Ovoid spores stain dark violet with Gram-Chromotrope staining and a darker equatorial band may be seen (more information at CDC and Medscape, and review by Lynne Garcia).
Microsporidial keratoconjunctivitis is particularly common during the monsoon, but is often misdiagnosed as atypical adenoviral keratoconjunctivitis. Upon slit lamp examination a greyish-white coarse diffuse superficial punctate keratitis is seen, generally in one eye only. The lesions are larger than that seen for viral disease and can be removed by debridement.
Dr Rohan Agashe and colleagues published a 3-year retrospective case series on 550 patients at an eye hospital in Tamil Nadu (South India). Of all conjunctivitis patients, just over 5% tested positive for microsporidia on Gram smear. Most patients had no obvious risk factors, apart from a minority who recalled having dust (12.7%) or an insect (2.4%) fall into the eye, and none used contact lenses. Good results were obtained by treating with 0.3% fluconazole eye drops, with >95% of patients reporting no loss of visual acuity.
Microsporidia spores with Gram-trichrome stain