EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Fungal keratitis, an infectious corneal disease caused by pathogenic fungal infections, is one of the most serious types of corneal infections, primarily due to its diagnosis and treatment complexity.¹ A plethora of pathogens have been documented as causative agents of fungal keratitis, and Fusarium and Aspergillus are the well-known prevalent etiological agents.² Infectious keratitis due to Alternaria alternata is a relatively uncommon condition, although there has been a modest rise in its prevalence. Here, we present a case of infectious keratitis with A alternata, with improvement after lamellar corneal transplant based on antifungal treatment.

Ethical approval was obtained from the Hospital Ethics Committee (approval No. Kelun-2023207K). Informed consent was obtained from the patient for this illustrative case.

A 56-year-old male patient was admitted to our hospital with redness, pain, and vision loss in the right eye. One month earlier, he had experienced ocular redness, pain, photophobia, tearing, and decreased visual acuity in the right eye without an obvious cause. There was a history of diabetes mellitus for more than 10 years. Ophthalmologic examination showed the following findings. Vision right eye was 0.04 (corrected to 0.08); vision left eye was 1.0. The right eye displayed mixed conjunctival congestion (++), with a 4 × 2-mm corneal ulcer located temporally inferiorly. Caseous necrotic tissue was firmly attached to the ulcerated area and difficult to remove (Figure 1); the rest of the cornea remained transparent.

Upon admission, corneal confocal microscopy revealed numerous fungal hyphae in the stromal layer of the right eye (Figure 2A). Local treatment included voriconazole eye drops (hourly), amphotericin B eye drops (hourly), and levofloxacin eye gel (3 times daily). Due to the proximity of the corneal ulcer to the pupil, which caused significant visual impairment, the patient underwent lamellar keratoplasty on the second day after admission. The surgery was successful. Microscopic morphology and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identified the pathogenic microorganism to be A alternata. Under the electron microscope, the conidia were ellipsoid, ovate, or obclavate, light brown to brown, with 0 to 6 transverse septa and 0 to 3 longitudinal septa, which were not constricted or slightly constricted at the septa ((Figure 2), B and C). Postoperatively, the patient received the following treatments: voriconazole eye drops (hourly), pranoprofen eye drops (4 times daily), sodium hyaluronate eye drops (4 times daily), levofloxacin eye gel (once nightly), and tacrolimus eye drops (2 times daily).

At predischarge physical examination, we observed the following details: vision right eye 0.03, mild congestion of the conjunctiva in the right eye, transparent corneal graft with secure sutures, slightly wrinkled posterior elastic layer of the cornea, normal depth of the anterior chamber with no aqueous flare, and a round pupil (Figure 3).

Fungal keratitis is a corneal infectious disease caused by pathogenic fungal infections and typically occurs under conditions such as corneal trauma, corneal surgery, chronic ocular surface diseases, local corti-costeroid application, or the use of contact lenses.³ In particular, in developing countries, the most prevalent causative agents of fungal keratitis are Fusarium and Aspergillus.² In contrast, fungal keratitis cases due to Curvularia lunata and A alternata infections are relatively rare, but there has been an upward trend in recent years.⁴

Notably, A alternata is a filamentous fungus belonging to the family of dark-colored fungi, which is a group of darkly pigmented molds widely distributed in soil, plants, food, and indoor air environments.⁵ This fungus grows and reproduces rapidly, with low nutrient requirements and strong spore-producing ability, factors that are the main reason for its strong pathogenicity, and can cause conditional infections such as skin infections and ocular mycoses.⁶ Fungal keratitis due to A alternata infection was first discovered in 1975, and A alternata is an uncommon causative agent of corneal infections.⁵ For example, in 2002, Zahra and colleagues reported a case of keratitis caused by A alternata in a male patient with diabetes mellitus following corneal trauma by a sharp object. The patient was treated with a topical amphotericin B solution and was discharged with improvement.⁷ Similarly, in 2023, Leite and colleagues reported a case of fungal keratitis caused by Streptomyces, which was treated with oral voriconazole and moxifloxacin hydrochloride eye drops, and the patient was discharged from the hospital in good condition.⁸

The clinical diagnosis of fungal keratitis is made by using a variety of diagnostic procedures, including the observation of corneal ulcer characteristics, the use of corneal confocal microscopy, and the analysis of results from corneal ulcer tissue scraping and culturing. Furthermore, the interpretation of these results can be further informed by a detailed history of corneal trauma. The patient described by Zahra and colleagues⁷ had reported no history of trauma; instead, the persistence of recurrent pain symptoms in the right eye and long-term medication due to diabetes mellitus, weakened tissue resistance to infections, and a decrease in local immunity led to an opportunistic infection by fungi. Clinically, corneal ulcers resulting from fungal infections frequently exhibit atypical early signs and symptoms, which can result in misdiagnosis. Consequently, corneal confocal microscopy and pathogenetic examination are important assets to guide early diagnosis and treatment, which can significantly improve the diagnostic accuracy rate and treatment success for patients with fungal keratitis. This finding is consistent with previous studies.^9,10

In conclusion, our case describes an episode of fungal keratitis caused by A alternata in a patient with long-standing diabetes mellitus and no evident history of trauma. We have demonstrated the impor-tance of early application of confocal microscopy and molecular biology identification of pathogenic microorganisms, coupled with prompt antifungal treatment and appropriate surgical intervention, in the successful management of fungal keratitis.

Volume: 23 Issue: 9 September 2025

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