[Neurometabolic diagnosis of mental retardation].

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.