Peripheral ulcerative keratitis is a rare but potentially devastating corneal emergency. It is characterized by crescentic-shaped peripheral ulceration and may involve the sclera and conjunctiva. The etiology includes immune-mediated systemic diseases such as granulomatosis polyangiitis and rheumatoid arthritis, immune-medicated ocular diseases such as Mooren’s ulcer and non-immune mediated conditions, especially infective etiology. A host of other conditions can also mimic this entity. The patient can present in the advanced stage with corneal perforation, necessitating emergency tectonic procedures.