We report on the first Polish patient diagnosed with the Aicardi-Goutières syndrome 5 (AGS5). AGS is caused by mutations in one of 9 genes (<i>TREX1</i>, <i>RNASEH2A</i>, <i>RNASEH2B</i>, <i>RNASEH2C</i>, <i>SAMHD1</i>, <i>ADAR</i>, <i>IFIH</i>, <i>LSM11</i>, <i>RNU7-1</i>) which stimulate the type I interferon response. The diagnosis was confirmed by identifying a compound heterozygous mutation p.(Phe165Ser)/p.(Gln235*) in the <i>SAMHD1</i> gene using whole-exome sequencing. The cystic lesions in the temporal lobes are an uncommon finding in the presented patient carrying a <i>SAMHD1</i> mutation. Reporting new cases expands the range of phenotypes and plays the crucial role in understanding the AGS pathogenesis and creates new therapy approaches.