The Diagnosis and Treatment of Peripheral Ulcerative Keratitis

Abstract

HE UNIQUE ANATOMIC and physiologT ical characteristics of the peripheral cornea explain its predilection to be involved in a variety of disorders.'.' Blood vessels and lymphatic channels from the adjacent conjunctiva and episclera enable diffusion into the cornea of some molecules, such as immunoglobulins and complement components. IgG and IgA are found in similar concentrations in the peripheral and central cornea; however, more IgM is found in the periphery, probably because its high molecular weight restricts diffusion into the central area.' Both classic and alternative pathway components of complement and its inhibitors have been demonstrated in normal human corneas; however, although most of the complement components have a ratio peripheral-to-central cornea of 1.2:1.0, C1 is denser in the periphery, with a ratio peripheral-to-central cornea of 5:l. The high molecular weight of C1, the recognition unit of the classic pathway, also may restrict its diffusion into the central a ~ e a . ~ ' ~ Normal human corneal epithelium contains small numbers of Langerhans' cells, with the greatest density at the limbus dropping to almost zero in the central cornea.6 The peripheral cornea also contains a reservoir of inflammatory cells, including neutrophils, eosinophils, lymphocytes, plasma cells, and mast cells.' The presence of IgM, C1, Langerhans' cells, and inflammatory cells makes the peripheral cornea more susceptible than the central cornea to ulceration in a wide variety of infectious and noninfectious local and systemic diseases, causing a specific entity named peripheral ulcerative keratitis (PUK) (Table 1). Whether it is the sequel of an infectious, trophic, traumatic, neurologic, dermatologic, anatomic, or autoimmune disease, PUK is always a local destructive process mediated by the final common pathway of collagenolytic and proteolytic enzyme release from inflammatory cells (Fig 1). PUK also may be the presenting manifestation of a potentially lethal systemic autoimmune vasculitic disease or may herald the onset of a potentially lethal systemic vasculitic process in a patient with an already known systemic disease. Early diagnosis and subsequent appropriate treatment may improve the ocular and systemic prognoses. We report our experience in the management of patients with noninfectious PUK emphasizing those historical, clinical, laboratory, and biopsy features that may be helpful in reaching a specific etiologic diagnosis. Recommendations for an approach to patients with noninfectious PUK are presented.