Histopathological examination of Acanthamoeba sclerokeratitis
A healthy 46-year-old man was referred to our hospital with severely reduced vision and severe pain to have his eye examined. He had been diagnosed with herpetic disciform keratitis at a local clinic 6 months earlier because of a ring infiltrate. Because of complications of iridocyclitis, he was treated with topical and systemic steroids along with acyclovir ointment. However, the symptoms and findings worsened, and he was referred to our hospital.\nOn his first visit, we learned that he had been wearing 1-day disposable soft contact lenses for several days. The visual acuity in his right eye was hand motion, and the cornea had a ring-shaped opacity with extensive epithelial defects (). A nodule was observed beneath the highly injected conjunctiva at the superior sclera close to the limbus (, arrow). Cysts of Acanthamoeba were identified in cultures of samples of the corneal abscess, and the patient was diagnosed with ASK. He was treated with oral itraconazole and topical micafungin and chlorhexidine (0.02%) hourly. The corneal region was debrided several times; however, the injection of the conjunctiva and sclera worsened, leading to necrotizing scleritis 1 month after the first examination (). An 8 mm-diameter ring-shaped abscess developed in the corneal lesion, and soon after that the cornea perforated (). Because he complained of severe pain and requested removal of the right eye, the eye was enucleated under general anesthesia.\nParaffin sections of the enucleated eye were examined histopathologically. Cysts of Acanthamoeba and polymor-phonuclear leukocytes (PMNLs) were observed throughout the corneal stroma, indicating an active invasion of the protozoan (). The anterior sclera in the limbal area was acutely inflamed with an infiltration of PMNLs, and an abscess was observed at the limbus ( and ). However, the sclera close to the ciliary body appeared different: granulation tissue consisting of congested blood vessels surrounded by macrophages and lymphocytes was observed in this area (). Interestingly, the signs of inflammation and granulation were not observed in the sclera posterior to the insertion of the rectus muscles or in the retina or choroid.