Patients with Down syndrome are at increased risk of juvenile arthritis. How different types of white blood cells contribute to the development of disease is not well understood and will be the focus of this project. This grant will support collection of blood samples from individuals with Down syndrome-associated arthritis which will allow for study of the role and function of white blood cells in these patients. We hope that better understanding of why and how individuals develop Down Syndrome-associated arthritis may provide insight to the best treatments for this patient population.