A 1-month female infant with hypotonia, feeding difficulties, facial dysmorphic signs, hepatomegaly and seizures was admitted to the neonatal intensive care unit. Brain magnetic resonance revealed regions of cortical dysplasia, diffuse polymicrogyria (prominent in the frontal and perisylvian cortex), reduction of white matter volume, delayed myelination and germinolytic cysts. The result of the plasma dosage of very long chain fatty acids was very high. Genetic testing revealed a homozygous pathogenetic mutation of the HSD17B4 gene. Thus, clinical features together with biochemical and genetic findings led to the diagnosis of Zellweger spectrum disorder (ZSD). ZSD is included in peroxisome biogenesis disorders. Before the biochemical and molecular bases had been fully determined, ZSD was defined by a continuum of three phenotypes: Zellweger syndrome, neonatal adrenoleukodystrophy and infantile Refsum disease. To identify a continuum of severity of the disease, the terms “severe,” “intermediate” and “milder” ZSD are now preferred. The individuals with ZSD mainly come to clinical attention in the newborn period or in childhood. Occasionally, the subtlety of symptoms delays diagnosis until adulthood. There is not specific therapy, in the severe ZSD prognosis is poor and survival is usually not beyond the first year of life.