Role of Interleukin 9 in Oral Lichen Planus Pathogenesis and Management

Abstract

Background:Lichen planus (LP) is a common chronic inflammatory condition that can affect skin and mucous membranes, including the oral mucosa. Because of the anatomic, physiologic and functional peculiarities of the oral cavity, the oral variant of LP (OLP) requires specific evaluations in terms of diagnosis and management. In this comprehensive review, we discuss the current developments in the understanding of the etiopathogenesis, clinical-pathologic presentation, and treatment of OLP, and provide follow-up recommendations informed by recent data on the malignant potential of the disease as well as health economics evaluations.The term lichen planus (LP) is derived from the Greek word lichen meaning tree moss and the Latin planus meaning flat. Erasmus Wilson first described the condition in 1869, as a chronic disease affecting the skin, scalp.nails, and mucosa, with possible rare malignant transfor-mation. LP may involve the hair follicles (lichenplanopilaris, resulting in scarring alopecia), nails and moreseldom, the eyes, urinary tract, nasal mucosa and larynx. Interleukin 9 has been implicated in numerous pathogenic processes of diseases, mainly allergic diseases as asthma and atopic dermatitis. IL-9 serum levels are elevated in patients with systemic lupus erythematosus, rheumatoid arthritis and systemic sclerosis but their clinical significance is still not completely understood. It has been debated if IL-9 has a role in the pathogenesis of these diseases, or if its presence is due to an epiphenomenon caused by a broad activation of inflammatory mechanisms, and this has made it difficult to define its function in the development of the disease.