Patients with LA were only included in this study if they (1) exhibited arthritis, (2) tested positive for Lyme antibodies, (3) indicated a positive western blot (WB) of five or more out of 10 Borrelia burgdorferi proteins by IgG antibodies or at least two of three B. burgdorferi proteins by IgM antibodies, and (4) at the age of 16 or below at the time of diagnosis. The gene discussed is CD40LG; the disease is arthritic joint disease.