A Case of Atypical Acanthamoeba Keratitis with Cruciate Stromal Infiltration

Purpose: To report a case of atypical Acanthamoeba keratitis (AK) with cruciate stromal infiltration, which was successfully treated. Case report: A 16-year-old woman with a history of intermittent soft contact lens wear was referred to our eye center. At presentation, her best-corrected visual acuity (BCVA) was 3/20 in the right eye. Slit lamp examination showed irregular epithelial infiltration, and mild edema in the cornea of the right eye. Topical antibiotics and antiviral agents were applied. After 1 week, her BCVA in the right eye decreased to counting fingers and epithelial infiltration was aggravated. Diffuse cruciate stromal infiltration newly developed. Under the presumptive diagnosis of AK, topical antibiotics and antiviral agents were stopped, and topical 0.02% chlorhexidine was started. After 2 weeks of treatment, the stromal infiltration decreased and culture was positive for Acanthamoeba species. After 3 months of treatment, the cornea was clear and her BCVA was 20/20 in the right eye. Conclusions: Atypical AK can present as cruciate stromal infiltration and can be treated successfully with topical 0.02% chlorhexidine.


Introduction
Acanthamoeba keratitis (AK) is a severe sight threatening corneal infection [1] and the number of patients with AK has increased dramatically in the last few decades [2]. In previous studies, AK primarily affected otherwise healthy contact lens wearers and young females [3].
Its symptoms are often nonspecific; severe pain, photophobia, and blurred vision may be present in bacterial, viral, and fungal keratitis [4]. Classic signs (eg, ring-shaped stromal infiltration, radial perineuritis, and limbitis) are not always present [5][6][7]. Diagnosis of AK is challenging because of these nonspecific symptoms and signs. Delays in proper diagnosis have been correlated with more extensive disease, greater likelihood of requiring keratoplasty, and worse final visual acuity [8].
Herein, we report a case of atypical AK with cruciate stromal infiltration, which was treated successfully with topical 0.02% chlorhexidine.

Case Report
A 16-year-old woman presented with a 2-week history of pain and decreased visual acuity in the right eye. The patient was an intermittent soft contact lens wearer. She had been treated 1 week previously for a herpes simplex keratitis (HSK) and had received topical antiviral ® Chungbuk, Korea) and ganciclovir ointment (Virgan ® ; Spectrum Théa Pharmaceuticals, Macclesfield, UK) four times per day with frequent instillation of artificial tears were prescribed.
After 1 week, her BCVA in right eye decreased to counting fingers. Epithelial infiltration and edema of the cornea were aggravated. Diffuse cruciate stromal infiltration was newly developed ( Figure 1A). We suspected AK, and performed corneal culture for Acanthamoeba. Topical gatifloxacin and ganciclovir ointments were stopped and topical 0.02% chlorhexidine was applied hourly. At 2 weeks, the epithelial and stromal infiltration of the cornea decreased ( Figure 1B) and her BCVA improved to 12/20 in the right eye. Corneal culture was positive for Acanthamoeba species. The topical treatment was continued.
At 1 month, the patient was more comfortable. Corneal infiltration was nearly absent, but faint stromal haze was persisted. Topical 0.02% chlorhexidine was tapered to 3 times a day. At 3 months, her cornea was clear ( Figure 1C) and BCVA was 20/20 in the right eye.

Discussion
This report emphasizes the need to suspect Acanthamoeba keratitis in contact lens wearers who present with cruciate stromal infiltration and progressively worsening keratitis that is unresponsive to usual antibiotics and antiviral therapy.
Eighty-five percent of AK cases are associated with contact lens use, with the improper use of tap water for contact lens care being the most significant risk factor [9]. Although all contact lens wearers are at risk of microbial keratitis, the epithelial thinning, overnight lens wear and corneal microtrauma that occurs with orthokeratology is considered especially hazardous [10]. Education regarding correct contact lens care is therefore extremely important in these patients.
AK can present with a dendritiform pattern of epithelial erosion that is frequently mistaken for HSK [11], and a nummular keratitis that may be confused with adenoviral keratitis [12]. However, the dendritiform pattern of AK does not have the terminal bulbs seen in HSK [13]. AK must be considered in all cases of presumed HSK or adenoviral keratitis in contact lens wearers. Features indicated of AK include pain out of proportion to slitlamp signs, contact lens contamination with tap water, poor response to topical antivirals [14].
Early AK includes epithelial disease such as punctate keratitis, pseudodendrites, and perineuritis without deep stromal involvement and anterior stromal disease such as subepithelial infiltrates [15]. Late AK findings include deep stromal infiltrates with or without epithelial disease and stromal ring infiltrates [16]. However, classic findings of AK such as perineuritis and ring infiltrate were only observed in about 20% of patients [15]. Jiang et al. reported salt-like dense infiltrate dots and groove-shaped corneal melting in 85.6% and 61.1% of patients, respectively [1].
In this study, we reported diffuse cruciate stromal infiltration as an atypical presentation of AK. The patient was treated with topical 0.02% chlorhexidine and visual function was successfully improved. Thus, ophthalmologists should maintain a high level of suspicion of AK in patients with cruciate stromal infiltration.