Solidarity plays a relevant role in rare diseases (RDs) research to create and enable research in the field. In Europe RDs are estimated to affect between 27 and 36 million people even though single RDs can count very few patients, making the contribution of everyone essential to reach solid results. Often RD research is initiated by patient groups devoting substantial time and resources to the scientific enterprise. In RD research solidarity is often evocated and expressed, in different ways and on different levels, so that it is possible to talk about "solidarities" played by different stakeholders and sometimes conflicting with each other. In this paper we describe different contexts in which solidarity is expressed and embedded in RD research, in particular the context of tight relationships between individuals and their families or in small communities/ethnic groups; among individuals suffering from different RDs and researchers working on a specific RD or a group of RDs, and within society at large. In all these cases the different types of solidarity should be balanced against each other and also against conflicting values. The request to a patient to share data and samples to increase scientific knowledge on the basis of solidarity values needs to be balanced against the need to protect her privacy and autonomy; the duty for a researcher to allow fair access to RD sample and data collections which were donated in a spirit of solidarity is balanced against the need to be competitive in the research world. In the Report "Solidarity. Reflections on an emerging concept in bioethics", the Nuffield Council of Bioethics defines solidarity as "shared practices reflecting a collective commitment to carry 'costs' (financial, social, emotional or otherwise) to assist others". Therefore, if a solidarity framework has to be solid and ethically sound it needs to be framed as a shared value, reflected in the different practices by all the stakeholders and be based on reciprocity (not one sided). The context of solidarity(ies) provides a solid base for framing the research endeavor as collectively valuable, not only for possible results of the research, but as intrinsic valid societal practice. This paper tries to draw the lessons on solidarity that we can derive from the RD world where "solidarities" have been part of the game for long time and are declined on many different levels.
Keywords: Biobanking; Data sharing; Governance; International research; Patient associations; Reciprocity; Solidarity.