Reverse Transcriptase Inhibitors in Aicardi Goutières Syndrome

Inclusion Criteria: * Molecular, neuroimaging, and clinical findings consistent with a diagnosis of AGS, with the exception of Double-stranded RNA-specific adenosine deaminase (ADAR1) and IFIH1, which are not postulated to result in nucleic acid accumulation * Evidence of interferon activation such as elevation of CSF neopterin/tetrahydrobiopterin measured on the first evaluation. * Ages 2-18 years (the age of 2 years is used because the drugs are FDA approved in children greater than 2 years) * Weight of at least 10 kg * Willingness to undergo serial lumbar punctures and blow draws for evaluation of laboratory based outcome measures * Willingness to abstain from initiating the use of immune modulating therapies including corticosteroids * Able to receive medications orally, by nasogastric (NG) tube or by Gastric (G)-tube * No concomitant illness which would preclude safe participation as judged by the investigator * Signed informed consent by the subject's legally acceptable representative * Negative testing for HIV * Negative testing for Hepatitis B * Concurrent enrollment in the Myelin Disorders Biorepository Project (MDBP, ClinicalTrials.gov NCT03047369) and willingness to undergo associated procedures Exclusion Criteria: * Age \< 2 years or \>18 years * Hepatic insufficiency with liver function tests greater than 3-times the upper limit of normal * Renal insufficiency with creatinine clearance \<60 * Significant malabsorption * Any clinical or laboratory abnormality o…