Sjögren's syndrome towards precision medicine: the challenge of harmonisation and integration of cohorts.

Primary Sjögren's syndrome (pSS) is a chronic, systemic autoimmune disease with diverse clinical picture and outcome. The disease affects primarily middle-aged females and involves the exocrine glands leading to dry mouth and eyes. When the disease extends beyond the exocrine glands (systemic form), certain extraglandular manifestations involving liver, kidney, lungs, peripheral nervous system and the skin may occur. Primary SS is considered the crossroad between autoimmunity and lymphoproliferation, since approximately 5% of patients develop NHL associated lymphomas. As with every chronic disease with complex aetiopathogenesis and clinical heterogeneity, pSS has certain unmet needs that have to be addressed: a) classification and stratification of patients; b) understanding the distinct pathogenetic mechanisms and clinical phenotypes; c) defining and interpreting the real needs of patients regarding the contemporary diagnostic and therapeutic approaches; d) physician and patients' training regarding the wide spectrum of the disease; e) creating common policies across European countries to evaluate and manage SS patients. To achieve these goals, an intense effort is being currently undertaken by the HarmonicSS consortium in order to harmonise and integrate the largest European cohorts of pSS patients. In this review, we present an overview of our perception and vision, as well as new issues arising from this project such as harmonisation protocols and procedures, data sharing principles and various ethical and legal issues originating from these approaches.