Rare diseases are defined as those that affect one person in 2,000, or around three million people in France. The majority of rare diseases are caused by genetics and tend to be severe when they begin in childhood. Autoimmune and autoinflammatory diseases, such as systemic lupus, juvenile dermatomyositis, and juvenile idiopathic arthritis, are examples of rare pediatric diseases. While autoimmune diseases are characterized by an inappropriate adaptive immune response, autoinflammatory diseases involve an excess of the innate immune response. The precise mechanisms of these diseases are not yet fully understood, but recent research has led to advances in their diagnosis and identification, particularly in early onset and familial forms. However, the rarity of these diseases and limited availability of biological samples pose significant challenges. This study aims to create a biological collection, which includes primary cells (PBMC), DNA, RNA, lymphoblastic lines, and serum, that will help identify genetic and immunological abnormalities in rare autoimmune and autoinflammatory diseases through various research projects.