Background Inherited metabolic disorders (IMDs) presenting in the newborn period are well described. Substantial numbers of these respond well to treatment but may otherwise be fatal. A high index of suspicion is necessary for an early diagnosis to prevent morbidity and mortality.

Objectives To study the spectrum of IMDs presenting in the newborn period in a region serving an ethnically diverse British population.

Methods Babies with a confirmed diagnosis of IMD presenting in the neonatal period were identified from the laboratory database. A retrospective case-note review of the clinical presentation and diagnosis was undertaken.

Results 29 neonates (14 female, 15 male) were identified. The mean age at presentation was 9 days (1 day–30 days, median 5 days). Of these 20% were identified due to persistent metabolic acidosis, 17% due to seizures, 17% due to family history, 14% due to hypoglycemia and 10% on newborn screening. Others presented with abnormal urine odour or persistently raised lactate (7%). The range of diagnoses included disorders of carbohydrate metabolism 20%, fat 24%, vitamins 14%, amino acids/organic acids 17% and mitochondria 10%. The most common diagnosis was MCAD. Consanguinity was present in 55%. The mean age at diagnosis was 60 days. 23/29 (79%) were amenable to treatment.

Conclusions This review highlights that substantial numbers of IMDs present in the newborn period with the majority in the first week of life. A high index of suspicion is necessary for an early diagnosis. Seizures, hypoglycemia, persistent metabolic acidosis and consanguinity are important clues to diagnosis.