Peripheral Ulcerative Keratitis

Excerpt

Peripheral ulcerative keratitis (PUK) is a disorder affecting the juxtalimbal cornea, classically presenting with epithelial defects and stromal lysis. This rare but severe inflammatory condition results from a complex interplay between host autoimmunity, the anatomy and physiology of the peripheral cornea, and environmental factors. The underlying cause could be local or systemic, infectious or noninfectious. PUK may be due to vasculitides or collagen vascular disease, rheumatoid arthritis, granulomatosis with polyangiitis (GPA), and systemic lupus erythematosus (SLE) can account for up to 53% of PUK cases. PUK with scleritis has a poor prognosis. Progressive stromal lysis can cause corneal perforation and, in patients with an underlying autoimmune disease, carries significant morbidity and mortality.

PUK without systemic association is known as Mooren ulcer (MU) and comprises 31.5% of PUK cases. Bowman first described this condition in 1849, followed by McKenzie in 1854, who called it an "ulcus roden" of the cornea. Mooren ulcer occurs in the absence of scleritis and is a diagnosis of exclusion. Clinical signs begin in the peripheral cornea and progress centrally and circumferentially, with a distinctive overhanging edge.

Quick recognition of PUK is crucial, as it can be the first presenting feature of a life-threatening systemic disease. Meticulous clinical investigation and interprofessional management are required to ensure safe patient outcomes.

The cornea has several layers, including the epithelium, Bowman membrane, stroma, Descemet membrane, and endothelium. The peripheral cornea has a rich vascular supply and an abundance of immune cells, making it more vulnerable to immune-mediated damage and inflammatory disorders like PUK. Most PUK cases arise in the setting of an autoimmune disorder. However, PUK may also result from infections, including herpes simplex virus and bacterial keratitis, ocular surface disorders, trauma, or surgical procedures. The natural history of PUK involves progression from peripheral corneal inflammation and thinning to ulceration, which can lead to perforation if left untreated. PUK may be staged based on the severity of corneal involvement. Without appropriate management, PUK can cause severe complications and may persist for months or even years with periods of remission and exacerbation.

The pattern of spread in PUK usually involves local extension along the peripheral cornea, with the potential for centripetal spread toward the central cornea in severe cases. PUK often presents unilaterally, and bilateral involvement is associated with systemic autoimmune disease. Investigations for PUK include slit-lamp examination with fluorescein staining to evaluate epithelial defects, microbial cultures to rule out infections, and testing for systemic autoimmune markers like antinuclear antibodies (ANA), rheumatoid factor, and antineutrophil cytoplasmic antibodies (ANCA). Anterior segment optical coherence tomography may also be used to assess corneal thickness.

Management of PUK involves both medical and surgical approaches. Topical steroids and immunomodulatory agents, such as cyclosporine and tacrolimus, control local inflammation, while systemic immunosuppressants, including methotrexate and biologics, are required for treating underlying autoimmune conditions. Surgical interventions, such as amniotic membrane transplantation and corneal transplantation, may be necessary in cases of severe corneal damage or perforation. Referral to a rheumatologist for managing associated systemic diseases is essential to ensure long-term control and prevent recurrence.

The prognosis for PUK varies with severity and the timeliness of treatment. If detected early and treated aggressively, patients can have a favorable outcome and preserve vision. However, delayed treatment may result in corneal perforation, permanent vision loss, and secondary infections.