Rare diseases (RD) constitute a health problem in modern societies, where chronic pathologies condition a large part of healthcare activity. On their own they are rare, but together they make up a wide range of disease patterns. The primary care paediatrician may be faced with a child or adolescent suffering from a RD, of which he/she will probably have little experience. The aspects to be considered in the management of these diseases are the following: a) guide the diagnostic process to establish it as early as possible; b) participate in the primary care team to improve diagnostic capacity, provide follow-up and manage the patient's therapeutic plan, as well as the RD registry of the health area; c) maintain a close relationship with the reference unit of the university hospital, and d) be aware of the genetic tests performed and the genetic diagnosis, inheritance and risk of familial recurrence.