The neonatal form of Aicardi-Goutières syndrome masquerading as congenital infection.

Aicardi-Goutières syndrome (AGS) is a rare, genetically-determined encephalopathy whose importance from a neonatology perspective is magnified because of the risk of misdiagnosis as the sequelae of congenital infection. Molecular advances have shown that AGS can be caused by mutations in any one of at least five genes (four of which have been identified). A recent genotype-phenotype study has shown that a neonatal form of the disease, highly reminiscent of congenital infection, is seen particularly with TREX1 mutations. It seems likely that the enzymes defective in AGS are involved in digesting endogenous nucleic acids (DNA and RNA) produced during normal cell replication, and that a failure of this removal results in inappropriate triggering of the innate immune system. This hypothesis explains the remarkable phenotypic overlap of AGS with congenital infection, where a similar interferon alpha mediated innate immune response is triggered by viral, as opposed to self, nucleic acids.