Update on Sjögren's syndrome autoimmune epithelitis: from classification to increased neoplasias

Sjögren's syndrome is a chronic inflammatory process that primarily involves the exocrine glands. Its clinical manifestations range from autoimmune exocrinopathy to extraglandular (systemic) involvement affecting the lungs, kidneys, blood vessels, and muscles; it can occur alone (primary Sjögren's syndrome) or in association with other autoimmune diseases (secondary Sjögren's syndrome). In recent years, clinical and laboratory observations have highlighted the central role of the epithelial cell and it has been suggested that the etiological name of the disease should be 'autoimmune epithelitis'. The extraglandular manifestations of the disease are divided in two groups: (1) lung, kidney (interstitial nephritis), and liver involvement as a result of lymphocytic invasion in epithelial tissues; and (2) skin vasculitis, peripheral neuropathy, and glomerulonephritis, with low C4 levels, which is the result of immune complex disease, are associated with increased morbidity and high risk for lymphoma. The diagnosis of the disease is based on the classification criteria, raised by the American-European Study Group and which have been built on the European preliminary classification criteria, developed in 1992. The association of Sjögren's syndrome with lymphoma is well documented as in approximately 5% of patients the benign autoimmune process is transformed into a lymphoid malignancy. The salivary extranodal marginal zone B-cell lymphomas of the mucosa-associated lymphoid tissue type are the most common lymphoma in Sjögren's syndrome. These tumors are antigen-stimulated B-cell lymphomas and are characterized by localized stage, indolent clinical course, and recurrence in other extranodal sites. Among the clinical and serological parameters that have been associated with lymphoma development in patients with Sjögren's syndrome, the presence of palpable purpura, low C4 and mixed monoclonal cryoglobulinemia constitute the main predictive markers; patients displaying these risk factors should be monitored closely. The purpose of this review is to discuss the clinical picture, the diagnostic procedure, and the malignant lymphoproliferation in the disease.