When the relative response to LPS and MTEP to LPS alone was compared between TD controls and children with FXS, GM-CSF ((−16.1% (−16.5 to 8.7%) versus −44.3% (−54.4 to −35.6%); P = 0.02) responses were reduced significantly more in children with FXS. The gene discussed is CSF2; the disease is fragile X syndrome.