Abstract
Developmental delay (DD) is common in paediatric practice and is present in 5-10% of children. Detailed evaluation can yield a definitive diagnosis in more than half of these cases and a substantial proportion of these are caused by chromosomal abnormalities and defects in the genes important for embryo development.
An inborn error of metabolism (IEM) can be identified in approximately 1% of patients with DD, but although a diagnosis of IEM is rare, accurate identification could make a big difference to the prognosis for the affected child, as well as counselling of the family and management of siblings. A diagnosis of IEM is more likely in the presence of additional abnormalities and developmental regression. The incidence of IEMs and the frequency of individual disorders vary depending on ethnicity.
IEMs can present at any age, but earlier diagnosis increases the chance of an improved prognosis, particularly in cases where treatments are available. As IEMs can affect any organ system, presentation can be variable and detailed clinical evaluation of patients with DD may direct further investigations. Particularly important clues can be found on dysmorphology, neuro-imaging and ophthalmic examinations.
There are a number of traditional approaches to classification of IEMs. These approaches may take into account the affected intracellular biochemical pathways, such as in urea cycle disorders, or individual organellar involvement, such as in mitochondrial diseases.
The strategy for investigation of inherited causes of DD, including novel molecular approaches to diagnosis, will be discussed.
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Further Reading
Moeschler et al. Pediatrics 2006; 117: 2304–2316
Cleary and Green. Arch Dis Child 2005; 90: 1128–1132
Sempere et al. J Inherit Metab Dis 2010; 33: 1–7
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Gissen, P. 10 Differential Diagnosis in Patients with Developmental Delay: Focus on Inborn Errors of Metabolism. Pediatr Res 68 (Suppl 1), 6–7 (2010). https://doi.org/10.1203/00006450-201011001-00010
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DOI: https://doi.org/10.1203/00006450-201011001-00010