Abstract
Sjögren’s syndrome (SS) is a chronic, progressive, inflammatory, autoimmune disease, characterized by the lymphocyte infiltration of exocrine glands, especially the lacrimal and salivary, with their consequent destruction. The onset of primary SS (pSS) may remain misunderstood for several years. It usually presents with different types of severity, e.g., dry eye and dry mouth symptoms, due to early involvement of the lacrimal and salivary glands, which may be associated with parotid enlargement and dry eye; keratoconjunctivitis sicca (KCS) is its most common ocular manifestation. It is still doubtful if the extent ocular surface manifestations are secondary to lacrimal or meibomian gland involvement or to the targeting of corneal and conjunctival autoantigens. SS is the most representative cause of aqueous deficient dry eye, and the primary role of the inflammatory process was evidenced. Recent scientific progress in understanding the numerous factors involved in the pathogenesis of pSS was registered, but the exact mechanisms involved still need to be clarified. The unquestionable role of both the innate and adaptive immune system, participating actively in the induction and evolution of the disease, was recognized. The ocular surface inflammation is a central mechanism in pSS leading to the decrease of lacrimal secretion and keratoconjunctival alterations. However, there are controversies about whether the ocular surface involvement is a direct autoimmune target or secondary to the inflammatory process in the lacrimal gland. In this review, we aimed to present actual knowledge relative to the pathogenesis of the pSS, considering the role of innate immunity, adaptive immunity, and genetics.
Highlights
Sjögren’s syndrome (SS) was described first in 1933 by a Swedish ophthalmologist, Henrik Sjögren
There is a paucity of data about the early pathogenic process; a viral infection involving the epithelial cells of exocrine glands—such as Epstein–Barr virus (EBV), cytomegalovirus (CMV), HIV, hepatitis C virus (HCV), coxsackievirus, human herpesvirus type 8 (HHV-8), and human trophic lymphocyte virus type 1 (HTLV-1)—is the most accredited hypothetical trigger factor of the initial autoimmune response, in addition to a specific genetic and environmental background [39,40,41,42]
Our understanding of ocular surface involvement in primary SS (pSS) is improving, based on several studies that have enlightened the molecular pathways at the basis of its pathogenic mechanism
Summary
Sjögren’s syndrome (SS) was described first in 1933 by a Swedish ophthalmologist, Henrik Sjögren. SS represents a chronic, progressive, inflammatory, autoimmune disease, characterized by the lymphocyte infiltration of exocrine glands, especially the lacrimal and salivary, with their consequent destruction [1,2,3,4]. As the majority of autoimmune diseases, it is more frequent in females, showing two peaks of incidence, the first between 20 and 40 years, and the second after menopause. The onset of pSS may remain misunderstood for several years. It usually presents with dry eye and dry mouth symptoms due to early involvement of the lacrimal and salivary glands, which may be associated with parotid enlargement [1,12,13]. In more than 30% of cases, systemic manifestations may occur, with involvement of the kidneys, lungs, skin, joints, and muscles [12]
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