1. Prepared by Sintawat Wangsiricharoen, MD and reviewed by Sean Zhang, MD, PhD

Clinical Vignette:
An adult patient with a past medical history of an autoimmune disease on systemic steroids and disease-modifying antirheumatic drugs (DMARDs) presents with corneal opacity for several months duration which started with sudden onset eye pain. The patient denied contact lens use and reported swimming in both fresh and cholorinated water. Prior work-ups included cultures which were negative for bacteria, fungi, and acanthamoeba. The patient had been treated with multiple regimens, including oral antiviral, topical steroids, and topical fortified antibiotics (vancomycin and amikacin). At presentation, vital signs were within normal limits and eye exam showed central opacity of the cornea with diffuse conjunctival injection. The patient received intrastromal voriconazole injection three times with much improvement and eventually underwent penetrating keratoplasty. The corneal tissue was sent to Surgical Pathology.

Microbiology Studies:
Bacterial, fungal, and amoeba cultures: No growth
HSV1/2, CMV, and VZV NATs: Not detected
Histopathology: See below









Question:
Which of the following is the most likely etiologic organism?