The inborn errors of Metabolism (IEM) are significantly interrelated with genetic abnormalities from carrier parents to their children. Physical and mental symptoms of IEM may appear with few days in affected newborns. Early diagnosis, genetic analysis of newborns, screening of future parents and nutritional treatment may help in reducing the chance to develop clinical symptoms of IEM . Patients and methods: This cross sectional study was included 65 cases with suspected IEM and done in Pediatrics Department, Zagazig University Hospitals. Results: In our study by comparing between cases included in the study we found that age presentation in cases of PKU was more during neonatal period 29 cases (80.5%) while in cases suspected metabolic or diagnosed metabolic non PKU age presentation was more during infancy 12 cases (66.67%) and 5 cases (45.45%). cases in PKU group were almost normal while the most common manifestation at the time of presentation in diagnosed non PKU group was sepsis-like manifestations (poor suckling) as well as disturbed conscious level each found in 5 cases (45.45%) followed by hepatosplenomegaly as well as delayed motor milestones in 4 cases (36.36%) , also in suspected metabolic group the most common manifestation was sepsis-like manifestations (poor suckling) in 10 cases (55.5%) followed by hepatosplenomegaly in 7 cases (38.89%). Conclusions: Inborn errors of metabolism (IEMs) are rare diseases worldwide and usually presented with poor suckling and lethargyand diagnosed during infancy period. Early diagnosis of IEMs with its proper treatment improve outcomes.