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Clinicopathologic Reports, Case Reports, and Small Case Series
August 2002

Infectious Keratitis Manifesting as a White Plaque on the Cornea

Arch Ophthalmol. 2002;120(8):1091-1093. doi:

We experienced a cluster of 3 cases of culture-proved infectious keratitis that, although caused by different organisms, each had a white plaque attached to the corneal surface without the typical findings associated with an infectious corneal ulcer.

Report of Case
Case 1

A 68-year-old woman visited our clinic complaining of a foreign body sensation and epiphora for 3 weeks in her right eye. She had no history of ocular disease or trauma. On slitlamp examination, a white plaque of gelatinous texture with sharply demarcated and elevated margins was seen on the nasal paracentral cornea in conjunction with a pterygium (Figure 1A). There was no epithelial defect, stromal infiltration around the plaque, or cellular reaction in the anterior chamber. Specimens were collected from the periphery of the plaque for smear and culture, and hourly administration of fortified antibiotic eyedrops was initiated. However, no resolution of the corneal plaque was observed for 1 week. Plaque removal was tried and the lesion was easily removed, leaving an almost clear stromal bed underneath. Assuming a diagnosis of a sterile corneal ulcer because of the quiet ocular findings and negative culture report, the fortified topical antibiotic regimen was changed to ofloxacin, 4 times daily, with hourly nonpreserved artificial tears. An epithelial defect at the plaque removal site persisted for 2 weeks, so we applied human amniotic membrane (HAM) and removed the pterygium. However, the epithelial defect slowly enlarged into the central cornea despite a lateral tarsorrhaphy. A white plaque reappeared on the epithelial defect during the next 3 months. Four months after her initial examination, we repeated removal of the corneal plaque and microbiologic testing from the stromal bed. The corneal plaque showed a roughened surface that appeared calcific in nature (Figure 1B) and was easily detached. The culture result disclosed Comamonas acidovorans with susceptibility to several antibiotics, including cefotaxime sodium, ceftriaxone sodium, ceftazidime, imipenem, and pefloxacin, although the patient did not return during the follow-up for treatment. Three months later, she sought care for a corneal perforation at another clinic and underwent evisceration (Figure 1C).

Figure 1.
A, A white plaque of gelatinous
texture with sharply demarcated and elevated margins is seen on the nasal
paracentral cornea in conjunction with a pterygium. B, The corneal plaque,
which slowly reappeared after the removal of the original plaque in part A,
exhibits a roughened surface and an apparently calcific nature and was easily
detached. C, Perforation is seen in the central cornea where the white plaque
was attached in part B.

A, A white plaque of gelatinous texture with sharply demarcated and elevated margins is seen on the nasal paracentral cornea in conjunction with a pterygium. B, The corneal plaque, which slowly reappeared after the removal of the original plaque in part A, exhibits a roughened surface and an apparently calcific nature and was easily detached. C, Perforation is seen in the central cornea where the white plaque was attached in part B.

Case 2

A 66-year-old woman was referred to us for a 1-month history of a foreign body sensation in her left eye. Initial slitlamp examination showed a white, calcific-appearing plaque with an elevated and well-outlined border (Figure 2). The cornea was otherwise quiet with no cellular reaction in the anterior chamber. The plaque was removed surgically and scraping for culture was performed from the underlying stromal bed. HAM was transplanted with the basement membrane layer up to prevent a persistent epithelial defect. Corneal epithelium, initially growing over the periphery of the HAM, failed to cover the center of the HAM, which showed signs of dissolution. At that time, pathologic examination of the plaque disclosed suspicious filamentous organisms embedded within severely degenerative tissue, and the microbiology laboratory reported the growth of Microsporum species. Treatment was begun with 0.15% amphotericin B eyedrops, and the HAM was covered slowly with epithelium, with no sign of recurrence at 3 months after discontinuation of treatment.

Figure 2.
A white plaque, apparently calcific
in nature, is seen with elevated and well-defined margins. Otherwise, the
cornea appears to be quiet and the anterior chamber is clear.

A white plaque, apparently calcific in nature, is seen with elevated and well-defined margins. Otherwise, the cornea appears to be quiet and the anterior chamber is clear.

Case 3

A 57-year-old man was referred for a possible corneal ulcer. He had complained of a gritty sensation in his left eye for 3 weeks. He also had a white and apparently calcific plaque, which had a well-demarcated and elevated margin (Figure 3A). A mild cellular reaction (1+) was seen in the anterior chamber. Excisional biopsy of the plaque, scrapings from the stromal bed for smear and culture, and transplantation of HAM over the denuded stroma were performed, followed by initiation of treatment with fortified antibiotics. One week later, the HAM started to dissolve, revealing a puslike fluid accumulation underneath. Natamycin eyedrops were added according to the biopsy result, which showed many filamentous fungal organisms within the plaque (Figure 3B). Acremonium species were cultured from the stromal bed. The corneal lesion improved gradually without any sequelae except for opacity that was limited to the HAM.

Figure 3.
A, A white and apparently calcific
plaque shows a well-demarcated and elevated margin. B, The filamentous fungal
organisms that were within the excised plaque (Gomori methenamine silver,
original magnification ×200).

A, A white and apparently calcific plaque shows a well-demarcated and elevated margin. B, The filamentous fungal organisms that were within the excised plaque (Gomori methenamine silver, original magnification ×200).

Comment

Although caused by different organisms, our 3 cases of infectious keratitis were characterized by the shared manifestations of a white corneal plaque, slow progression, and mild clinical inflammatory features relative to most cases of infectious keratitis. Entrapment of less virulent microorganisms within the plaques, which were formed by an unknown mechanism, might be the reason for the slow and mild clinical features. However, corneal perforation is possible if the correct diagnosis and proper management are delayed as in case 1, where pathological examination of the plaque was not performed owing to our inexperience.

We performed immediate HAM transplantation in cases 2 and 3 because of the problem of the persistent epithelial defect in case 1, where the initial negative microbiologic report influenced us not to be suspicious of an infection in cases 2 and 3. In retrospect, we do not think that HAM transplantation was essential to healing. In fact, the HAM might have acted to some extent as a barrier against the penetration of antimicrobial eyedrops. The best management option would probably be an excisional biopsy of the plaque and the administration of antibiotics guided by an in vitro drug sensitivity test, without HAM transplantation. HAM could be used later if an epithelial defect persists after treatment of the infectious component.

As for the cultured microorganisms in this report, C acidovorans is a ubiquitous gram-negative rod and is generally considered nonpathogenic. Keratitis caused by C acidovorans has been rarely reported, and no reported cases showed clinical features that were similar to our case 1.1,2Microsporum, although one of the most common causative organisms for dermatomycoses, has not been reported to cause infectious keratitis to the best of our knowledge. Acremonium-caused keratitis is also rare compared with other fungal infections.3 Further microbiologic evidence may be needed to confirm the true role of these organisms in corneal ulcers. We believe, however, that corneal perforation, as in case 1, and a healing response to antifungal drops, as in cases 2 and 3, suggest the infectious nature whatever the actual causative organism might have been.

In conclusion, these were all cases of indolent corneal infections that manifested as white plaques on the cornea. It is important to perform culture and histopathologic studies on the plaque in addition to the stromal bed for this kind of atypical infectious keratitis.

Corresponding author and reprints: Beom-Jin Cho, MD, Department of Ophthalmology, College of Medicine, University of Ulsan, Asan Medical Center, #388-1, Poongnap-dong, Songpa-gu, Seoul 138-040, South Korea.

References
1.
Stonecipher  KGJensen  HGKastl  PRFaulkner  ARowsey  JJ Ocular infections associated with Comamonas acidovoransAm J Ophthalmol. 1991;11246- 49
2.
Brinser  JHTorczynski  E Unusual Pseudomonas corneal ulcers. Am J Ophthalmol. 1977;84462- 466
3.
Kennedy  SMShankland  GSLee  WRSekundo  W Keratitis due to the fungus Acremonium (Cephalosporium). Eye. 1994;8 (pt 6) 692- 694Article
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