Introduction This database includes the raw data on clinical characteristics of patients with Aicardi Goutières Syndrome carrying the homozygous p.A177T RNASEH2B, which is the most common variant associated to the syndrome and the variant associated to the most striking phenotypic variability. Methods Retrospective natural history study, designed to describe a cohort of patients with homozygous p.A177T RNASEH2B with variable degrees of phenotypic expression. Patients will be stratified according to disease severity in order to identify possible predictive factors of long term outcomes. Results (in brief) Our cohort confirm the significant intra-genetic cohort variability of patients carrying this specific mutation. In our case series, only few and aspecific characteristics have been found to be related to prognosis: irritability at disease onset, age at onset, presence of startle reactions