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[Neurometabolic diagnosis of mental retardation]
1Pediatric Neurology, South Texas Specialists Center, MacAllen 78503, USA.
Abstract:
Eighty-five percent of mentally retarded people have mild mental retardation (MR). Severe MR has a probable or definitive causes in 80% of cases. 2/3 are prenatal, 1/6 perinatal and 1/6 postnatal. Metabolic disorders may manifest as MR and its progressive nature often is not observed at the time of evaluation. MR is a prominent finding of many hereditary metabolic diseases, but only a fraction of MR seen in daily practice is due to inborn errors of metabolism. Medical conditions may present as MR without major extraneurological changes. In the investigation of MR, developmental milestones of affected children as well as detailed physical and neurological exam looking for physical characteristics, and performance of routine and special screening tests should be done. The metabolic screening tests (urine and/or blood) is very helpful. Use of tandem MS or acylcarnitine profile in blood for the diagnosis of organic acidurias and aminoacidurias can be done in 3 minutes per blood sample, with more than 20 conditions simultaneously tested. Blood spots in filter paper, once dried, are stable for weeks and can be sent by regular air mail, with low processing costs. Its future as a mass screening tool seems promising.
Insights
Mild mental retardation (MR) affects 85% of individuals. While severe MR often has identifiable causes, metabolic disorders can present as MR, necessitating comprehensive screening. Early detection through metabolic tests is crucial.
Area of Science:
- Medical Genetics
- Developmental Pediatrics
- Clinical Biochemistry
Context:
- Mental retardation (MR) is a significant concern, with mild MR comprising 85% of cases.
- Severe MR has identifiable causes in 80% of cases, often linked to prenatal, perinatal, or postnatal factors.
- Metabolic disorders can manifest as MR, sometimes without obvious extraneurological signs, and their progressive nature may be missed.
Purpose:
- To highlight the role of metabolic disorders in causing mental retardation (MR).
- To emphasize the importance of thorough investigation for MR, including developmental milestones, physical/neurological exams, and screening tests.
- To introduce advanced metabolic screening techniques for diagnosing MR.
Summary:
- Investigating mental retardation (MR) requires assessing developmental progress, conducting detailed physical and neurological examinations, and performing routine and specialized screening tests.
- Metabolic screening tests, including urine and blood analyses, are highly valuable in identifying potential causes of MR.
- Techniques like tandem mass spectrometry (MS) or acylcarnitine profiling can rapidly screen for over 20 metabolic conditions (organic acidurias, aminoacidurias) from a single blood sample.
Impact:
- Rapid diagnostic tools like tandem MS and acylcarnitine profiling offer efficient and cost-effective methods for identifying metabolic causes of MR.
- Dried blood spots on filter paper are stable and suitable for mailed screening, reducing logistical challenges.
- These advancements hold promise for the future implementation of mass screening programs for metabolic disorders contributing to MR.