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 Table of Contents  
Year : 2021  |  Volume : 1  |  Issue : 4  |  Page : 651-653

Successful medical management of bilateral microsporidial stromal keratitis: A case report and review of literature

1 Cornea and Anterior Segment Services, The Cornea Institute, LV Prasad Eye Institute, GMR Varalakshmi Campus, Visakhapatnam, Andhra Pradesh, India
2 Ocular Microbiology Service, LV Prasad Eye Institute, GMR Varalakshmi Campus, Visakhapatnam, Andhra Pradesh, India

Date of Submission25-Nov-2020
Date of Acceptance06-May-2021
Date of Web Publication09-Oct-2021

Correspondence Address:
Dr. Merle Fernandes
Cornea and Anterior Segment Service, The Cornea Institute, L V Prasad Eye Institute, Hanumanthawaka Jn, Visakhapatnam - 530 040, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijo.IJO_3219_20

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An 81-year-old gentleman with a vague history of dust falling into the eyes presented with a white lesion in the left eye for 5 months. Both eyes showed two foci of central dense stromal infiltrates with keratic precipitates. Suspecting herpes simplex virus (HSV) keratouveitis, topical steroids, and antiviral eye ointment were started. A month later, he developed unilateral microsporidial keratoconjunctivitis with persistent bilateral deep stromal keratitis. The corneal scrapings revealed microsporidial spores on 10% Potassium hydroxide (KOH)with Calcofluor White Stain. Topical 1% voriconazole eye drops for 4 months in the right eye, a combination of 1% voriconazole and Natamycin eye drops for 9 months in the left eye and oral albendazole 400 mg twice daily for 3 weeks resulted in complete resolution. There were no recurrences over 1 year. We present a literature review of the medical management of microsporidial stromal keratitis highlighting our case with bilateral disease successfully managed medically with antifungal therapy.

Keywords: Antifungal therapy, bilateral microsporidial stromal keratitis, microsporidial stromal keratitis, voriconazole

How to cite this article:
Sharma S, Madduri B, Mohan N, Fernandes M. Successful medical management of bilateral microsporidial stromal keratitis: A case report and review of literature. Indian J Ophthalmol Case Rep 2021;1:651-3

How to cite this URL:
Sharma S, Madduri B, Mohan N, Fernandes M. Successful medical management of bilateral microsporidial stromal keratitis: A case report and review of literature. Indian J Ophthalmol Case Rep [serial online] 2021 [cited 2021 Oct 26];1:651-3. Available from: https://www.ijoreports.in/text.asp?2021/1/4/651/327667

Microsporidial stromal keratitis is a rare clinical entity associated with poor prognosis. The two major lacunae in the management of these cases are its diagnosis and treatment.[1] Therapy is often delayed due to misdiagnosis as herpes simplex virus (HSV) stromal immune keratitis[1] or delayed identification of the organism.[1],[2],[3] Medical treatment often fails, ultimately requiring penetrating keratoplasty, which has subsequently become the treatment of choice.[1],[4]

  Case Report Top

An elderly gentleman presented with a white spot on the black portion of his left eye for 5 months. Best-corrected visual acuity (BCVA) was 20/30 and 20/100 in the right and left eyes, respectively. Both eyes had two foci of mid-stromal infiltrate, surrounding stromal edema without an overlying epithelial defect, and keratic precipitates in the left eye [Figure 1]a and [Figure 1]b. A diagnosis of bilateral HSV keratouveitis was made. Topical steroids and acyclovir eye ointment were started. No clinical improvement was noted and at 1 month, the right eye had diffuse, coarse superficial epithelial keratopathy with an epithelial defect. The left eye had a small epithelial defect with underlying stromal infiltrate [Figure 2]a and [Figure 2]b. The diagnosis was revised to bilateral microsporidial keratitis (epithelial + stromal). Medications were discontinued. Bilateral corneal scraping showed gram-positive oval-shaped microsporidia, confirmed on 1% acid-fast staining [Figure 2]c and [Figure 2]d.
Figure 1: (a and b) Slit-lamp image using sclerotic scatter showing a single focus of mid-stromal infiltrate in the right eye (arrow) and two foci of mid-stromal infiltrates in the left eye (arrows) with surrounding stromal edema and keratic precipitates in the left eye

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Figure 2: (a) Slit-lamp photo of the right eye using sclerotic scatter showing coarse superficial punctate keratitis (SPK) in the central and peripheral cornea with the nasal paracentral mid-stromal infiltrate and (inset) showing fluorescein stain with coarse punctate epitheliopathy and a typical “stuck-on” appearance (b) Slit-lamp photo of the left eye using sclerotic scatter showing the two dense mid-stromal infiltrates (1.4 mm × 2 mm). The superior edge of the upper infiltrate is denser. The epithelial defect, not clearly seen without fluorescein stain, is overlying the upper infiltrate (c) About 10% KOH Calcofluor white wet mount of the corneal scraping of the right eye (40X) showing fluorescent oval-shaped spores with the appearance of a “starry sky” (d) Gram stain in oil immersion (100X) of corneal scraping of the left eye, showing three gram-positive oval-shaped spores with faintly visible polar staining (black arrows)

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Topical voriconazole (1%) eye drop hourly and oral albendazole (400 mg) twice daily for 3 weeks were started. Investigation for human immunodeficiency virus (HIV) was negative. A favorable response was seen in both the eyes with complete resolution of infiltrate in the right eye over 4 months, following which topical medications were discontinued. The left eye had minimal edema and infiltrate, hence topical 1% voriconazole was continued 3 hourly. Four months later, he developed pain and redness in the left eye for 4 days duration while on topical voriconazole eye drops. The left eye had an epithelial defect (1 mm × 1.5 mm) with underlying infiltrate (2.5 mm × 2.2 mm), significant thinning, streak hypopyon, and rubeosis iridis [Figure 3]a. Suspecting either microsporidial keratitis exacerbation or a secondary infection, a repeated corneal scraping showed microsporidia (reconfirmed with 1% acid-fast stain) and gram-positive bacilli on Gram stain [Figure 3]b, [Figure 3]c, [Figure 3]d identified as Corynebacterium amycolatum species on cultures. Topical antibiotics were started and topical voriconazole was stepped up to hourly. A course of oral albendazole was restarted. In view of significant thinning, cyanoacrylate tissue adhesive with a bandage contact lens was applied. Natamycin 5% eye drops, added after a month due to extremely slow response with voriconazole, resulted in perceptible improvement. The lesion showed complete scarring 5 months later, and topical medications were discontinued. Unfortunately, he experienced a drop in the vision in the left eye due to a closed funnel retinal detachment noted on ultrasound B scan. He completed 1 year of follow-up after complete resolution without any recurrence [Figure 4]a and [Figure 4]b.
Figure 3: (a) Diffuse slit-lamp photograph of the left eye showing diffuse conjunctival congestion, 360° superficial vascularization, and a dense infiltrate superiorly with a smaller infiltrate inferno nasally and scarring in the central cornea. A <1 mm hypopyon is noted in the anterior chamber. (b) About 10% KOH Calcofluor white wet mount of the corneal scraping of the right eye (40X) showing a few fluorescent oval-shaped spores (c) Gram stain in oil immersion (100X) of corneal scraping of the left eye, showing 1 gram-positive oval-shaped spore with visible polar stain (black arrow) and three short gram-positive bacilli (white arrows) (d) About 1% acid-fast stain (100X) showing an intracellular acid-fast microsporidial spore (arrow)

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Figure 4: (a and b) Slit-lamp photo of the right and left eyes showing complete resolution with a scar and dense vascularization. No recurrences were noted over a 1-year follow-up

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  Discussion Top

Microsporidia are small, oval, spore-forming obligate intracellular parasites, closely related to fungi, and are pervasive in vertebrates and invertebrates.[4] Ocular microsporidiosis can either occur in isolation or as a part of systemic involvement.[4]

The ocular manifestations include superficial punctate keratoconjunctivitis and stromal keratitis,[4] predominantly governed by the genus involved and the immune status of the patient. Keratoconjunctivitis, caused by genus Encephalitozoon, is a superficial self-limiting variant.[4] The stromal microsporidiosis caused by Nosema (renamed Vittaforma) and Microsporidium, has a more indolent course and poor response to medical treatment.[4] Microsporidial stromal keratitis can occur after keratoconjunctivitis in an immunocompromised patient.[5] Systemic immunosuppression as well as topical corticosteroids are risk factors for the development of epithelial keratoconjunctivitis.[4] We speculate that topical steroids for a month could have predisposed to development of epithelial disease in our patient. Species identification using specific immunofluorescence techniques, electron microscopy, or polymerase chain reaction (PCR)[4] would have helped us to confirm the organism causing epithelial and stromal disease. Contaminated water is a possible source for bilateral disease; however, no such history was elicited.

Stromal microsporidiosis is often misdiagnosed as HSV stromal immune keratitis and shows a poor response to steroids and antivirals.[1] This led us to reevaluate and revise our diagnosis to microsporidial stromal keratitis which was then confirmed on microbiology.

Most microsporidial stromal keratitis cases require penetrating keratoplasty.[1] There are a few case reports describing successful medical therapy for stromal microsporidiosis [Table 1].[5],[6],[7]
Table 1: Synopsis of Outcome of Microsporidial Stromal Keratitis Successfully Treated with Medication

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Considering that microsporidia are closely related to fungus, there is a role of antifungals as possible therapy for stromal microsporidiosis.[4] Voriconazole possibly inhibits the spore filament extrusion[8] and albendazole inhibits microtubule polymerization of the microsporidia.[9] The role of Natamycin is unclear since it is not known to have any activity against microsporidia.

Animal studies have shown that topically administered voriconazole (1%) has good ocular penetration and attains aqueous concentration exceeding the minimum inhibitory concentration required to inhibit the growth of 90% of organisms of most fungal pathogens.[10] Similar data are not available for microsporidia since they does not grow in culture.

Medical management was considered as the initial treatment of choice in our patient considering his age and bilateral involvement, avoiding the risks associated with penetrating keratoplasty.

  Conclusion Top

To the best of our knowledge, this is the first report of successful management of bilateral stromal microsporidial keratitis using topical antifungals (voriconazole 1% and Natamycin 1%) for a prolonged duration with a short course of oral albendazole. This therapy may be recommended for stromal microsporidiosis before attempting penetrating keratoplasty.

Financial support and sponsorship

This work was supported by Hyderabad Eye Research Foundation.

Conflicts of interest

There are no conflicts of interest.

  References Top

Sabhapandit S, Murthy SI, Garg P. Microsporidial stromal keratitis Clinical features, unique diagnostic criteria, and treatment outcomes in a large case series. Cornea 2016;35:1569-74.  Back to cited text no. 1
Coca M, Kim J, Shenoy S, Chévez-Barrios P, Chévez-Barrios P, Kapur M. Microsporidial stromal keratitis: Successful treatment with topical voriconazole and oral itraconazole. Cureus 2016;8:e934.  Back to cited text no. 2
Grillo LM, Epstein LJ, Donnenfeld ED, Perry HD. Late-onset microsporidia keratitis in femtosecond astigmatic keratotomy after laser-assisted phacoemulsification. Cornea 2018;37:1471-3.  Back to cited text no. 3
Sharma S, Das S, Joseph J, Vemuganti GK, Murthy S. Microsporidial keratitis: Need for increased awareness. Surv Ophthalmol 2011;56:1-22.  Back to cited text no. 4
Badenoch PR, Coster DJ, Sadlon TA, Klebe S, Stirling JW, Jaunzems AE, et al. Deep microsporidial keratitis after keratoconjunctivitis. Clin Exp Ophthalmol 2011;39:577-80.  Back to cited text no. 5
Sagoo MS, Mehta J, Hau S, Irion LD, Curry A, Bonshek RE, et al. Microsporidium stromal keratitis: In vivo confocal findings. Cornea 2007;26:870-3.  Back to cited text no. 6
Sangit VA, Murthy SI, Garg P. Microsporidial stromal keratitis successfully treated with medical therapy: A case report. Cornea 2011;30:1264-6.  Back to cited text no. 7
Leitch GJ, He Q Wallace S, Visvesvara GS. Inhibition of the spore filament extrusion of the microsporidium, E hellem, isolated from an AIDS patient. J Eukaryot Microbiol 1993;40:711-7.  Back to cited text no. 8
Han B, Weiss LM. Therapeutic targets for the treatment of microsporidiosis in humans. Expert Opin Ther Targets 2018;22:903-15.  Back to cited text no. 9
Vemulakonda GA, Hariprasad SM, Mieler WF, Prince RA, Shah GK, Van Gelder RN. Aqueous and vitreous concentrations following topical administration of 1% voriconazole in humans. Arch Ophthalmol 2008;126:18-22.  Back to cited text no. 10


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]


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