Inborn Error of
Metabolism (IEM) are group of genetic disorders that affect the metabolic
pathways in neonates after birth. IEM are due to genetic mutations in the genes
coding a key enzyme or cofactor involved in metabolism, thus producing an
incomplete or non-functional enzyme causing a block in a metabolic pathway.
These genetic disorders have clinically significant consequences and if left
undiagnosed and untreated may cause infant mortality or death in early
childhood. A new born baby with IEM is normal however after external intake of
dietary proteins or drugs, the disorder starts to manifests and the predominant
symptoms are seen as lethargy, acidosis, ketosis, poor feeding, seizures,
failure to thrive or coma(Udani & Kumta, 2005). The
inheritance pattern of IEMs is autosomal recessive where the defective gene is
present in both parents and can be passed on from generation to generation.
The incidence of IEMs
varies in different ethnic groups and geographical regions with higher incidences
in regions with greater occurrence of consanguineous marriages. The most common
disorder observed in India are Congenital Hypothyroidism, Phenylketonuria (PKU),
Biotindase Deficiency, Glucose 6 Phosphate Dehydrogenase Deficiency (G6PD), Congenital
Adrenal Hyperplasia (CAH), Galactosemia (GAL), and Maple Syrup Urine Disease
(MSUD)The prevalence of Inborn Error of Metabolism in India is one in 2497
newborns, congenital hypothyroidism incidence is 2.1 per 1000 and
G6PD deficiency is 2-7.8%. Worldwide, the incidence of IEM is more than 1/1000(Fatima, Kumar Sonkar, Tripathi, & Singh, 2017).
A metabolic approach is
used to diagnose an IEM in a new born. Biofluids and dried bloodspots are taken
and investigated using technology namely Radioimmunoassay, ELISA,
fluoroimmunossay, Tandem Mass Spectroscopy, and NMR.
1.1 New Born Screening
New Born Screening is
an important test done for a neonate for early detection and diagnosis of
metabolic, genetic and endocrine disorders. NBS is a simple and inexpensive
test which enables early prevention and treatment of diseases and help the baby
to lead a normal life and reach their full potential. It is considered as a
standard practice to detect significant number of IEMs at birth in most