Lessons from diseases mimicking Sjögren's syndrome.

Sjögren's syndrome (SS) is a systemic autoimmune disease that mainly affects the exocrine glands and usually presents as persistent dryness of the mouth and eyes because of functional impairment of the salivary and lacrimal glands. The histological hallmark is a focal lymphocytic infiltration of the exocrine glands, and the spectrum of the disease extends from an organ-specific autoimmune disease (autoimmune exocrinopathy) to a systemic process with diverse extraglandular manifestations. In the absence of an associated systemic autoimmune disease, patients with this condition are classified as having primary SS. The differential diagnosis includes processes that specifically involve the exocrine glands. On the one hand, some chronic viral infections may induce lymphocytic infiltration of the exocrine glands, in some cases indistinguishable from that observed in primary SS. On the other hand, some processes may mimic the clinical picture of SS through nonlymphocytic infiltration of the exocrine glands. This review focuses on these two groups of diseases that mimic SS (infections and infiltrating processes).