Microsporidial keratitis: Literature review and report of 2 cases in a tertiary eye care center

Case Report: The Use of In Vivo Confocal Microscopy for Diagnosis and Monitoring in a Rare Case of Ancaliia algerae Microsporidial Keratitis in New South Wales, Australia

We describe the successful management of Ancaliia Algerae microsporidial keratitis in an immunosuppressed 54-year-old woman with refractory linear IgA disease. The case highlights the challenges in diagnosis and management of this infection in immunocompromised individuals and emphasizes the usefulness of in vivo confocal microscopy as a novel, noninvasive tool to aid in the diagnosis and monitoring of microsporidial keratitis. We also discuss the possible mode of acquisition of this rare infection.

Case Report: Microsporidial Endophthalmitis after Penetrating Eye Trauma

SIGNIFICANCE

In the recent past, there are increasing publications on microsporidia affecting the cornea in Asian population. However, microsporidia-causing endophthalmitis has been rarely reported. This report intends to draw the attention of eye care professionals to consider microsporidia as a differential diagnosis in cases of keratitis or endophthalmitis after ocular trauma.

PURPOSE

The purpose of this study was to report a case of microsporidial endophthalmitis after corneal tear in an otherwise healthy patient.

CASE REPORT

A 62-year-old healthy gentleman sustained injury to the left eye cornea with the tip of a soiled and wet screw driver. Two days after the corneal tear suturing, he complained of pain. On examination, circumcorneal congestion with hypopyon of 2 mm in height was present. Vitreous tap and intravitreal antibiotics were injected. Vitreous tap showed microsporidia. Pars plana vitrectomy was performed. His vision improved to 6/12.

CONCLUSIONS

Microsporidia are an emerging cause of stromal keratitis. In the recent past, there has been an increase in microsporidial keratitis in both immunocompetent and immunocompromised individuals. History of trauma especially in rainy season and exposure to soil are reported risk factors. This is a case report on microsporidia-causing endophthalmitis after corneal tear repair. Ophthalmologists and optometrists should be aware of the possibility of microsporidia as a potential pathogen causing stromal keratitis or endophthalmitis in a setting of ocular trauma. Early treatment can result in good visual recovery.

Microsporidial Stromal Keratitis: Epidemiological Features, Slit-Lamp Biomicroscopic Characteristics, and Therapy

PURPOSE

Microsporidial stromal keratitis is a rare form of infectious keratitis, with only 7 cases reported in the United States to date. This study was performed to evaluate risk factors, clinical features, and response to therapy.

METHODS

A retrospective review of the medical records of all patients diagnosed with microsporidial stromal keratitis seen in the practices of the authors between 1999 and 2020 was performed. Diagnosis was determined by cytology or histopathology in corneal specimens. Risk factors, presence or absence of distinctive clinical features, and response to medical and surgical therapies were recorded.

RESULTS

Nine patients-7M:2F, aged 7 to 99 years-with microsporidial stromal keratitis were identified. Exposures to recreational water and hymenopteran insect bites, both epidemiologically linked risk factors for systemic microsporidial infection, were identified in our patients. Presence of stromal edema with features of disciform keratitis and a distinctive granular keratitis were observed in 6 of 9 and 5 of 9 patients, respectively. Poor response to medical therapy was noted. Penetrating keratoplasty was effective in curing the infection. Final visual acuity was 20/40 or better in 6 of 9 patients.

CONCLUSIONS

In patients with slowly progressive keratitis, history of exposure to recreational water or hymenopteran insects should be sought. In patients with corneal edema consistent with disciform keratitis, with evolution to a granular keratitis, microsporidia should be considered in the differential diagnosis. In cases of established microsporidial stromal keratitis, penetrating keratoplasty should be considered if prompt response to medical therapy is not noted.

Stromal microsporidial keratitis successfully treated with medical therapy

Purpose

To report a case of severe stromal microsporidal keratitis successfully treated with oral albendazole and topical voriconazole.

Observations

A 71-year-old man presented with progressive vision loss and corneal opacification for one year. Initial visual acuity was counting fingers attributed to a dense subepithelial opacification. Confocal microscopy and subsequent corneal biopsy lead to the diagnosis of microsporidial keratitis. The patient completed a four-week course of oral albendazole and topical voriconazole which resulted in resolution of the corneal opacification and improvement in visual acuity to 20/250.

Conclusions and Importance

A four-week course of oral albendazole and topical voriconazole was an effective treatment for severe stromal microsporidial keratitis.

Microsporidial Keratitis Related to Water Exposure: A Case Series

The objective of this retrospective study was to present a series of cases involving the rare ocular disease of microsporidia keratitis treated at a private practice clinic and describe the details regarding specific water exposure, clinical course, voriconazole treatment, and increased prevalence of this infection in Augusta, Georgia, USA. Our analysis was based on the accumulated data from all patients (n=15) diagnosed with microsporidia keratitis at our private practice clinic; the clinical course of three cases is discussed in detail in this article. Specific environmental exposures were documented in 10 patients. All patients self-reported that they had no acquired immunodeficiency. In all cases, patients had complete resolution of active symptoms after receiving treatment with 1-2% topical voriconazole, with an approximate average primary treatment duration of 40.1 ± 17.1 days (median: 40 days, range: 14-70 days). None of the patients reported any clinically significant adverse effects from therapy.

There have been increasing reports about this emerging infectious pathogen, particularly in Asia. However, there is limited data in the literature on the etiology, pathogenesis, and treatment of microsporidia-caused ophthalmic diseases. In this case series, we highlight the strong correlation of our patients' condition with specific types of water exposure in the USA as well as the complete resolution of active disease in all our patients as a result of monotherapy with topical voriconazole.

Microsporidial stromal keratitis in an immunocompromised patient: Successful management with medical therapy

Microsporidial stromal keratitis is refractory to topical drugs and is classically described in immunocompetent hosts. A 55-year-old patient with renal transplant and oral immunosuppressants, presented with a 15-day history of redness, pain, and diminution of vision in the right eye. Slit-lamp examination revealed epithelial defect and mid-stromal infiltrate. On corneal scraping, microsporidial spores were observed. The patient was started on topical 0.02% polyhexamethylene biguanide (PHMB) and the infiltrate resolved after 6 weeks of initiation of topical therapy.

A Narrative Review of Microsporidial Infections of the Cornea

Microsporidia are a rare and commonly misdiagnosed cause of corneal infection, accounting for approximately 0.4% of cases of microbial keratitis in some populations. Ocular microsporidiosis most often presents as either microsporidial keratoconjunctivitis (MKC) or microsporidial stromal keratitis (MSK). Though these two clinical entities exhibit similar symptomology, they are distinguished from one another by the time course for disease progression, findings on slit-lamp examination, and response to medical therapy. This review summarizes the current literature on the etiology and clinical presentation of microsporidial infections of the cornea and highlights ongoing developments in available diagnostic modalities and treatment regimens.

Microsporidial keratopathy in two dogs

A microsporidial keratopathy is described in two dogs. Both dogs presented with a unilateral stromal keratopathy characterized by multifocal coalescing opacities, and the diagnosis was made on histopathologic examination of keratectomy specimens. Transmission electron microscopy (TEM) on formalin-fixed, paraffin-embedded corneal tissue was performed in one dog, and the morphologic features were consistent with Nosema species infection. Both dogs were initially diagnosed and treated by superficial keratectomy. One dog received additional antifungal medication and underwent a penetrating keratoplasty following local recurrence two years later. No other systemic lesions attributable to the microsporidial infection were identified clinically. The clinical and diagnostic pathology findings, treatment, and follow-up are discussed.

Review of Contact Lens-Related Complications

The purpose of this article is to provide a review of existing literature describing complications with contemporary contact lenses and their management. It is envisioned that this will serve as a useful summary of noninfectious and infectious complications associated with contact lens wear.

Late-Onset Microsporidial Keratitis in Femtosecond Astigmatic Keratotomy After Laser-Assisted Phacoemulsification

PURPOSE

To present a case of microsporidial keratitis in a femtosecond laser-created astigmatic keratotomy (AK) incision.

METHODS

Case report.

RESULTS

A 65-year-old Middle Eastern man presented 2 months after uncomplicated femtosecond laser-assisted cataract surgery (FLACS) and AK with mildly decreased vision and corneal edema in the operative eye. Shortly after treatment with topical corticosteroids, a fulminant corneal infiltrate manifested along the temporal arcuate incision. Multiple corneal scrapings sent for laboratory analysis were inconclusive. Two weeks after the initial presentation, a deep tissue sample was obtained using a 27-gauge cannula passed within the arcuate incision. The gram stain was directly observed, revealing intracellular microsporidial spores. The patient was treated with oral albendazole 400 mg once daily over 2 weeks and topical voriconazole 1% and fumagillin 3 mg/mL eye drops over 10 weeks. During this course, visual function steadily recovered as the infiltrate coalesced and ocular inflammation subsided.

CONCLUSIONS

This is the first reported case of microsporidial keratitis presenting as a late-onset infection after femtosecond laser-assisted AK.

Molecular surveillance of Vittaforma-like microsporidia by a small-volume procedure in drinking water source in Taiwan: evidence for diverse and emergent pathogens

Vittaforma corneae belongs to microsporidia, which include over 1500 species of opportunistic obligate intracellular fungi infecting almost all known animal taxa. Although outbreaks of ocular infections caused by waterborne V. corneae have been reported in recent years, little is known about the occurrence of this pathogen in aquatic environments. In this study, 50 water samples from rivers and reservoirs around Taiwan in two seasons were analyzed to explore the presence of this pathogen in natural aquatic environments. A high detection rate of Vittaforma-like amplicons (94%; 47/50) was observed in the water samples when examined by nested PCR with primer pairs specific to the small ribosomal subunit (SSU) rRNA gene. After electrophoresis, many lanes showed multiband patterns with expected molecular weights. After confirmation by DNA sequencing and by sequence alignment in the NCBI database, we identified a variety of Vittaforma-like microsporidia with weak sequence similarity, with approximately 85% identity to V. corneae, thus indicating high diversity of microsporidia in aquatic environments. Phylogenetic analysis showed clear-cut microsporidian clade classification and indicated that the most Vittaforma-like microsporidia in this study belong to clade IV and cluster into four major groups. The first group is similar to the microsporidia associated with ocular microsporidiosis. The second group is associated with the diarrheal pathogens, whereas the third and fourth groups are a novel group and a zoonotic group, respectively. This study provides abundant sequencing information, which will be useful for future molecular biological studies on microsporidia. Because microsporidia are important pathogens of animals and humans, it is urgently necessary to determine via a survey whether there are species with potential threats that have not yet been revealed.

Microsporidia and 'the art of living together'

Parasitism, aptly defined as one of the 'living-together' strategies (Trager, 1986), presents a dynamic system in which the parasite and its host are under evolutionary pressure to evolve new and specific adaptations, thus enabling the coexistence of the two closely interacting partners. Microsporidia are very frequently encountered obligatory intracellular protistan parasites that can infect both animals and some protists and are a consummate example of various aspects of the 'living-together' strategy. Microsporidia, relatives of fungi in the superkingdom Opisthokonta, belong to the relatively small group of parasites for which the host cell cytoplasm is the site of both reproduction and maturation. The structural and physiological reduction of their vegetative stage, together with the manipulation of host cell physiology, enables microsporidia to live in the cytosolic environment for most of their life cycle in a way resembling endocytobionts. The ability to form structurally complex spores and the invention and assembly of a unique injection mechanism enable microsporidia to disperse within host tissues and between host organisms, resulting in long-lasting infections. Microsporidia have adapted their genomes to the intracellular way of life, evolved strategies how to obtain nutrients directly from the host and how to manipulate not only the infected cells, but also the hosts themselves. The enormous variability of host organisms and their tissues provide microsporidian parasites a virtually limitless terrain for diversification and ecological expansion. This review attempts to present a general overview of microsporidia, emphasising some less known and/or more recently discovered facets of their biology.