Autoantibodies to cerebellum in children with autism associate with behavior

► Plasma autoantibodies for 45 kDa cerebellar protein associate with an autism diagnosis. ► Plasma autoantibodies for 62 kDa protein associate with broader diagnosis of ASD. ► Children with autoantibodies had worse behavioral scores than children without them. ► Few familial associations found for brain-targeted antibodies in children and mothers. ► Antibodies may be markers for specific behavioral characteristics of autism.