The phases and natural history of Sjögren's disease: a new model for an old disease?

Sjögren's disease (SjD) is an archetypal and heterogenous autoimmune disorder that is characterised by exocrine glandular dysfunction. A proportion of patients develop severe extra-glandular manifestations such as cryoglobulinaemia, and have an increased risk of lymphoma, both of which can adversely affect quality of life and occasion mortality. As with most autoimmune disorders, the pathogenesis is poorly understood, difficult to predict and frustratingly, there is a lack of targeted therapies to cure this disease. We review the disease manifestations of SjD and propose a staged model for understanding the evolution of pathology. In longitudinal studies, most patients remain relatively stable in terms of their laboratory and clinical parameters. However, in the setting of various risk factors, a proportion of patients develop severe symptoms and/or lymphoma. We discuss potential underlying mechanisms for disease progression and the strengths and limitations of using a staged model to correlate the pathogenesis and spectrum of manifestations in SjD. Ultimately, understanding how and why some patients remain relatively stable, while others progress and develop florid systemic disease and a fraction develop lymphoma, is key to developing preventative and therapeutic treatments.