Toxoplasmosis was detected in 11 (24.4%) autistic children through the ELISA [10 (22.2%) IgG + /IgM − and 1 (2.2%) IgG + /IgM +]; however, RT-PCR assay recorded only 1 positive case (2.2%), while it was detected in 10 (22.2%) control children through ELISA [9 (20%) IgG + /IgM − and 1 (2.2%) IgG + /IgM +] and 1 (2.2%) by RT-PCR. The gene discussed is CD40LG; the disease is toxoplasmosis.