Interestingly, one form of Aicardi-Goutières Syndrome caused by activating mutations in IFIH1, the gene that encodes MDA5, alters the function of MDA5 so mutant MDA5 now recognizes Alu:Alu inverted repeats with imperfect sequence homology. The gene discussed is IFIH1; the disease is Aicardi-Goutières syndrome.