<h4>Objective</h4>To determine if multiplex autoantibody arrays can identify novel biomarker signatures in children with one or multiple autoimmune diseases (polyautoimmunity).<h4>Methods</h4>Plasma collected from children (18 years or younger) in the Boston Children's Hospital Precision Link Biobank for Health Discovery between January 2007 and June 2021 was analyzed using a microarray with 120 autoantigens associated with various autoimmune diseases to assess for both immunoglobulin G (IgG) and A (IgA) autoantibodies. This evidence concerns the gene CD79A and autoimmune disease.