Severe corneal melting with necrotic sloughing in Acanthamoeba keratitis mimicking corneal endotheliitis

BACKGROUND: Acanthamoeba keratitis (AK) is a sight-threatening corneal infection that may initially lack typical epithelial or perineural findings and mimic other infectious or inflammatory anterior segment disorders. Endotheliitis-like presentations of AK with stromal edema, keratic precipitates, Descemet membrane folds, and anterior chamber inflammation have been reported, but progression to severe stromal necrosis with spontaneous sloughing of necrotic corneal tissue is rarely documented. CASE PRESENTATION: A 48-year-old contact lens wearer presented with right eye pain, redness, and decreased vision. Initial examination at a local clinic revealed anterior chamber inflammation without epithelial defects, radial keratoneuritis, or a ring infiltrate, and topical betamethasone was started before referral. At referral (0 weeks; 12 days after symptom onset), slit-lamp examination revealed diffuse stromal edema, fine keratic precipitates, Descemet membrane folds, and anterior chamber inflammation, closely mimicking viral corneal endotheliitis. Aqueous humor polymerase chain reaction for human herpesviruses 1-8 was negative. Because viral endotheliitis or noninfectious anterior uveitis was considered, topical corticosteroids and systemic prednisolone were administered (initially 30 mg/day and was gradually tapered). During follow-up, the clinical appearance evolved toward AK, and anti-infective therapy was revised. Corneal scraping was performed, but direct microscopy and bacterial and fungal cultures were negative. PCR testing of a corneal scraping specimen for Acanthamoeba, bacteria, and fungi was negative. Despite treatment, stromal necrosis progressed to severe corneal melting. At 34 weeks after referral, necrotic corneal tissue spontaneously sloughed as a sequestrum and was submitted for pathological evaluation. Hematoxylin and eosin and periodic acid-Schiff staining revealed necrotic corneal stromal tissue with inflammatory cell infiltration and multiple double-walled cystic structures consistent with Acanthamoeba cysts, confirming AK. CONCLUSIONS: This case illustrates a diagnostically challenging form of AK that initially mimicked corneal endotheliitis, yielded negative scraping-based microbiological tests, and was ultimately confirmed by histopathologic examination of spontaneously sloughed necrotic stromal tissue. Severe AK rarely manifests as necrotic stromal sequestration and spontaneous sloughing, in addition to the more commonly recognized destructive outcomes such as corneal thinning, perforation, or keratoplasty-requiring disease. Repeated diagnostic reassessment is important in contact lens wearers with atypical endotheliitis-like keratitis, particularly when the disease progresses despite antiviral or anti-inflammatory therapy.