English abstract
Inborn errors of metabolism (IEMs) are permanent inherited biochemical disorders. They are inherited mostly through autosomal recessive modes, which have been credited to the high rate of consanguinity in the Omani society. They are a rare group of genetic disorders that can produce serious clinical consequences for an affected neonate or young infant. In general; an inborn error of metabolism is caused by lack of a functional enzyme, transmembrane transporter, or similar protein, which then results in blockage of the corresponding metabolic pathway. There may be an accumulation of metabolites prior to the metabolic block, and/or deficiency in the ultimate product(s) of the pathway. Consequently if undiagnosed and untreated, these disorders can cause irreversible mental retardation, physical disability, neurological damage or even fatality. Early detection and an accurate diagnosis are very important for achieving a rapid medical intervention and favorable patient outcome.
The aims of this study were to examine the status of IEMs at SQUH in order to shed light on the types and patterns of IEMs in Oman, as well as, their prevalence, using tandem mass spectrometry (MS/MS) which permits the detection and quantification of many IEMs in a single blood spot and a single analytical run. Information about the onset of symptoms and signs in patients was gathered and an assay cutoff values and concentrations for amino acids and acylcarnitines for Omanis were established and compared with other published data.
A retrospective review of IEMs detected by MS/MS during 1998 – 2008 at SQUH revealed the diagnosis of IEMs in 111 patients. These were divided into 27 different metabolic diseases and categorized into three main groups: Amino acids and urea cycle disorders, Organic acid disorders, and Fatty acid oxidation disorders. The review revealed that IEMs are over-represented in babies born to consanguineous parents, which is consistent with the recessive autosomal inheritance of IEMs. The pattern of diagnosed diseases appears different from that observed in Caucasian and other Arab groups.
In a prospective study, ten new patients with IEMs were diagnosed in selective screening of 150 high-risk babies. In a pilot newborn screening study, three newborns were positive out of 1780 screened babies. This gives a prevalence of IEMs of 1:600, which is two times higher than that reported in Saudi Arabia and Qatar and eight times higher than North European figures.
In conclusion, this study shows that several types of TEMs reported internationally were also prevalent in Oman and, therefore, warrants the development of a nationwide screening program as well as development of systematic prevention programs for such genetic disorders.
