Acanthamoeba Keratitis Presenting With Marginal Keratitis – A Disastrous Case Report

To present a case of refractory amoebic keratitis with bacterial and viral co-infection.

This case report involves a challenging patient referred from a local medical department to Taipei City Hospital Zhong Xing Branch, Taipei, Taiwan. The treatment course spanned from January 2019 to January 2020.

A 63-year-old male patient presented with progressing foreign body sensation in his left eye for 1 week. This occurred after he drunk on roadside and injured his eye. Examination revealed perilimbal corneal infiltration with a suspected pseudodendritic epithelial defect.

Under the impression of marginal keratitis combined with herpes infection, antibacterial and antiviral agents was initiated. However, the ocular pain and lesion progressed. Smear with gram stain suspected the presence of amoeba pathogens, and was confirmed with Merthiolate-Iodine-Formaldehyde (MIF) stain and polymerase chain reaction (PCR) test. Topical Chlorhexidine, Polyhexamethylene biguanide hydrochloride, Brolene and oral voriconazole were then added. Further smear showed co-infection involving both bacteria and yeast-like pathogen. Viral PCR confirmed the presence of Herpes virus. After four months, he was discharged after condition improved.

However, the corneal lesions relapsed and continued to progress, accompanied by thinning, hyphema, and cataract. Acanthamoeba cysts are still observed in the deep stroma throughout the course of treatment. The patient underwent lamellar keratectomy to remove the infected tissue and subsequently required emergent penetrating keratoplasty due to corneal perforation after 11 months of treatment. Stitch abscess and stromal infiltration from graft-host junction were soon occurred. The patient, unable to endure the pain of the treatment, has decided to undergo enucleation.

Amoebic keratitis poses a diagnostic challenge due to similarities or co-infection with other pathogens. Suspect amoebic infection, especially with atypical manifestations and disproportionate pain. A detailed observation of the Gram stain may enhance the detection and differentiation of amoebas, providing a foundation for the selection of therapeutic drugs and further investigations.

In cases of amoebic keratitis with limbal involvement, current topical and systemic anti-amoebic agents may have a positive effect but hard to eradicate the amoebic cyst. Corneal transplantation is often inadequate for addressing such situations. We look forward to the development of new medications in the future to assist in controlling amoebic keratitis.