Inborn Errors of Metabolism-Approach to Diagnosis and Management in Neonates

Inborn errors of metabolism (IEM), otherwise known as inherited metabolic disorders (IMD), are individually rare, but collectively common. IEM pose a challenge to diagnosis, as neonates present with nonspecific signs. A high index of suspicion is essential. Knowledge on clinical presentation may be life saving, especially for conditions that are treatable. It is important for the first-line physicians not to miss treatable disorders. Simplified classification and algorithmic approach help in the clinical setting. This article describes the classification of IEM into three groups, namely group 1 - intoxication disorders, group 2 - energy defects, and group 3 - storage disorders. Clinical presentations of IEM in the neonatal period, a quick guide to the diagnosis with the help of baseline investigations (glucose, arterial blood gas, lactate, ammonia, and ketone abbreviated as GALAK), a tabulated guide to the diagnosis with the help of tandem mass spectrometry (TMS), and gas chromatography and mass spectrometry (GCMS) are summarized in this article. Four principles of therapy that include substrate reduction, provision of deficient metabolites, disposal of toxic metabolites, and increase in enzyme activity are elaborated with particular stress to the diet management. In addition, a list of medications used in the treatment of different disorders classified according to Society for the Study of IEM (SSIEM) is presented.