Histopathology-based diagnosis of Mooren's ulcer concealed beneath the pterygium on eye

Mooren's ulcer (MU) is a chronic and painful ulcerative keratitis that is difficult to diagnose, especially when concealed beneath the pterygium, which is a common, benign, wedge-shaped, fleshy tissue growth of the conjunctiva extending onto the cornea. The coexistence of MU and pterygium is extremely rare. A 41-year-old man presented with a 2-month history of unprovoked redness, pain, and blurred vision in the right eye. Corneal epithelial defects around the pterygium head were noted upon slit-lamp examination and fluorescein staining. The patient was initially misdiagnosed with a corneal epithelial defect and pterygium. The initial treatments with anti-inflammatory and corneal epithelial growth promotion tear agents failed. Anterior segment optical coherence tomography (AS-OCT) showed corneal stromal lysis thinning, and in vivo confocal microscopy (IVCM) revealed marked inflammatory cell infiltration and stromal degeneration. We suspected the pathology was an immune-related or tumor-related corneal ulcer. The MU concealed beneath the pterygium was diagnosed by histopathological examination of a biopsy specimen that presented typical localized loss of the corneal epithelium and Bowman's layer, stromal degeneration, and inflammatory cell infiltration. Finally, we performed lamellar keratoplasty (LKP) combined with pterygium excision surgery. The patient recovered with no complications or recurrence during the 1-year follow-up period. Few cases of MU concealed beneath the pterygium have been reported. It is beneficial to rule out the pathological changes concealed beneath the pterygium, combined with multiple means of examination such as slit-lamp examination, AS-OCT, and IVCM. A histopathological examination should be performed to establish a diagnosis.