Understanding Vernal Keratoconjunctivitis: Beyond Allergic Mechanisms

Abstract

Vernal keratoconjunctivitis (VKC) is a chronic, recurrent, inflammatory disease of the cornea and conjunctiva mostly affecting boys in prepubertal age. VKC recurrence is characterized by intense symptoms of itching, redness, and photophobia associated with corneal damage, impairment of visual function, and quality of life. The pathogenesis of VKC has not yet been completely understood, and it is still controversial. In fact, VKC is considered an ocular allergic disease due to the involvement of immunoglobulin E, eosinophils, and mast cells, and of a lymphocyte T-helper type 2 reaction. However, approximately half of VKC patients have negative allergological history and testing, suggesting that other pathogenic mechanisms participate in VKC development and severity. Specifically, evidence suggests that genetic, endocrine, neuronal factors and an imbalance of innate immunity are involved in the pathogenesis of VKC. The purpose of this review is to summarize evidence on the pathogenic role of innate immunity, neuroimmune reaction, and hormonal changes in VKC. Increasing understanding of the pathogenic mechanisms behind VKC may lead to the identification of novel biomarkers for diagnosis and/or potential therapeutic targets in order to improve the management of this challenging condition.

Keywords: allergic disease; innate immunity; neuroinflammation; sex hormones; vernal keratoconjunctivitis.

Figure 1

(a) Tarsal VKC with upper tarsal giant papillary reaction, (b) limbal VKC with limbal papillary reaction and the so-called Horner-Trantas dots.

Figure 2

Corneal epithelial defect in a patient with VKC.

Figure 3

Allergic reaction represents the main pathogenic factor of VKC; however, several sources of evidence show that innate immunity and neuroinflammatory response, as well as genetic, hormonal, and environmental factors, also participate in the development and severity of VKC.