A 16-day-old male infant was hospitalized because of recurrent fever with rash for 14 days, unresponsive to anti-infective therapy. Clinical features included persistently elevated inflammatory markers, multisystem involvement (skin, nervous system, and heart), and facial dysmorphism (frontal bossing and saddle nose). Genetic testing revealed a de novo heterozygous, likely pathogenic NLRP3 variant (c.2269G>A, p.Gly757Arg). In combination with clinical findings, neonatal-onset multisystem inflammatory disease (NOMID) was diagnosed. Prenatal ultrasonography showed absence of the ductus venosus and bilateral ventriculomegaly, expanding the prenatal sonographic phenotype of NOMID. This case suggests that in neonates with unexplained fever, rash, poor response to anti-infective treatment, and facial dysmorphism, the presence of prenatal ultrasound abnormalities such as absent ductus venosus or ventriculomegaly should raise clinical suspicion for NOMID, and early genetic testing is recommended to confirm the diagnosis and guide intervention. Citation:Chinese Journal of Contemporary Pediatrics, 2026, 28(1): 111-114