Activation of astrocytes caused by elevated levels of proinflammatory cytokines in the DS brain36 and increased astrocytic expression of S100B (a protein encoded by the gene on chromosome 21) could provide an explanation for increased plasma levels of GFAP in the present study and previously reported high CSF levels of another astrocytic marker, YKL-40, in asymptomatic DS.7 The gene discussed is S100B; the disease is Dravet syndrome.