Objectives: To analyze the clinical and laboratory data of neonates diagnosed with Zellweger syndrome and to estimate the incidence of the syndrome. Methods: The databases of four institutions that admitted newborns diagnosed with Zellweger syndrome to intensive care units between January 2013 and December 2016 were examined. Results: A total of 105,887 live babies were born in the four centers during the study period. Seven were diagnosed with Zellweger syndrome; the incidence was thus

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... . Birth weights were 2,200 -3,300 g. Six cases were born to consanguineous parents. Dysmorphic findings, respiratory failure, and hypotonia were evident in all patients. Hepatomegaly was apparent in four cases, congenital cardiac defects in four, characteristic cerebral magnetic resonance imaging findings in four, renal cysts in five, hepatic cysts in three, and splenomegaly in one. PEX1 mutations were identified in three patients, and one mutation was novel. Conclusions: The incidences of Zellweger syndrome and cardiac disease were higher than reported previously, being (to the best of our knowledge) among the highest reported worldwide. This is the first time that such incidences have been calculated in Turkey. The syndrome is more common in regions where consanguineous marriage rates are higher.