Neonatal-onset multisystem inflammatory disorder (NOMID) is a rare congenital disorder characterized by a neonatal-onset urticarial rash, arthropathy, recurrent fevers, and central nervous system disease. We report 3 cases in which patients presented with neonatal-onset urticarial eruption and other organ involvement of varying severity. Genetic testing of 2 of these patients revealed previously unreported genetic mutations in exon 3 of the CIAS1 gene, a recently discovered member of the pyrin gene family. The third patient did not demonstrate a CIAS1 mutation. These cases illustrate the genetic basis of NOMID, an autoinflammatory disorder, and highlight the emerging role of the pyrin gene family in the regulation of nuclear factor kappaB signaling and other pathways involved in inflammation and apoptosis.