A positive antinuclear antibody test means that antibodies are present in the blood that are targeting structures within the nucleus of cells. This can happen for a variety of reasons, but viral infections and certain seizure medications are possible causes. In some cases, a positive antinuclear antibody test can be indicative of an autoimmune disease, such as lupus or rheumatoid arthritis. Autoimmune diseases occurs when the body's immune system mistakenly attacks healthy tissue. This can cause