Equal rights in autoimmunity: is Sjögren's syndrome ever 'secondary'?

Abstract

Sjögren's syndrome (SjS) accompanied by other systemic autoimmune rheumatic connective tissue diseases has historically been termed 'secondary' in contrast to 'primary' SjS as a standalone entity. However, it is a matter of a long-standing debate whether the prefixes 'primary' and 'secondary', including a temporal component, are obsolete in the terminology of SjS. We review the history and the pathophysiological, chronological, genetic, histological and clinical data underlying the concept of 'secondary' SjS. There are important unintended consequences of the nomenclature; notably 'secondary' SjS has been much less researched and is often excluded from clinical trials. We argue for further research, a change in terminology and more stringent classification. Further we highlight possible opportunities for trials in SjS and other systemic autoimmune diseases that might contribute to an advance in care for all patients with SjS.

Keywords: RA; SLE; Sjögren’s syndrome; anti-Ro antibodies; clinical trials; genetics; histology; salivary glands; systemic sclerosis.