Although these phenomena have not been linked, it is plausible that impaired IGF-1+ microglial function in the maintenance of striatal neurons might be causative of neuronal loss observed in Tourette syndrome (Figure 2). Hdc-KO mice have not been reported to develop spontaneous reduction of striatal interneurons; however, this might happen in aging mice or young mice subjected to immune challenge. The gene discussed is IGF1; the disease is Tourette syndrome.