Sjögren syndrome is a chronic, systemic autoimmune disease that is common and has important life-altering and severe effects on those with the disease. Despite these facts, the disease has received relatively less attention in terms of research (both laboratory-based and clinical) and in the clinic than related illnesses, such as systemic lupus erythematosus or rheumatoid arthritis. Among the lay public, just about everyone knows someone with lupus it seems, but not so for Sjögren syndrome. As of 23 January 2016, a search of the OVID Medline search engine shows 47,492 articles coded with the MESH Subject Heading “systemic lupus erythematosus” and 86,158 with the MESH Subject Heading “rheumatoid arthritis”, but only 10,809 articles coded with the MESH Subject Heading “Sjögren’s syndrome”. But, perhaps, as evidenced in this issue of Rheumatic Disease Clinics of North America , Sjögren syndrome is making up some ground in the early twenty-first century.
As documented by Xavier Mariett and his colleagues, one way in which research in Sjögren is progressing is the study of biologic agents. Furthermore, as noted in this article, there are many ongoing studies with agents tested in other diseases as well as agents that will first be studied in Sjögren syndrome. However, several important trials have either failed or not met their primary endpoint. The provocative article by Robert Fox outlines why it might be that clinical trials in Sjögren syndrome are fraught with difficulty.
There are some clear advantages to the study of Sjögren syndrome. The most obvious of these is the ability of investigators to directly study the affected organs, which lend themselves to biopsy easily. In fact, as emphasized by Barone and colleagues in this issue, the salivary glands are not only the main site of damage in the disease but also the central hub of the pathologic processes. On the other hand, study of the disease has disadvantages. These include difficulty in clinical diagnosis and research classification. The use of both ultrasound and parotid gland biopsy is reviewed in this issue. Neither are part of present research classification criteria, and neither are ready to be performed widely. Additional research in these areas, however, may lead to important clinical and research use of these techniques. Laboratory-based research to understand the pathologic and etiologic features of the disease is being pursued vigorously as demonstrated in articles reviewing advances in genetics, autoantibodies, and proteomics. Finally, clinical guidelines have recently been issued for treatment of dental and oral disease as well as certain aspects of the systemic illness that occur among those with Sjögren syndrome. Vivino and colleagues have summarized all three of these initial treatment guidelines.
Not included in this issue is a discussion of new classification criteria that are being developed in an alliance of the ACR and EULAR. These new criteria should be published in 2016 and will hopefully provide a unified set of criteria that can be applied to research (including clinical trials) in the disease. I am confident that this issue concentrating on Sjögren syndrome relates the excitement in the field as research and clinical care advance rapidly.