[The contribution made by genetics and neurometabolic studies to the diagnosis of mental retardation].

INTRODUCTION AND DEVELOPMENT: Mental retardation (MR) is a disability that is frequently found in children and adolescents. It can be caused by a large number of factors and this makes it a serious challenge for the neuropaediatrician, who has to choose from among a wide range of complementary tests in order to be able to screen it. Diagnostic algorithms can be useful in accomplishing this objective, but they are only really valuable as a guide. Recent advances in genetic and molecular techniques have been of great use in pinpointing anomalies that conventional cytology is unable to identify. Techniques such as comparative genomic hybridisation (CGH) array analysis, multiplex ligation probe amplification (MLPA) or sequencing as well as association studies by means of single nucleotide polymorphisms stand out for their importance in the aetiological diagnosis of MR with and without syndromes.

CONCLUSIONS: Some inborn errors of metabolism, such as urea cycle disorders, creatine transport deficiency, 4-hydroxybutyric aciduria, adenylosuccinate lyase deficit, Sanfilippo disease or certain congenital errors in the glycosylation of proteins may course with unspecified MR and must be taken into account in some situations. Performing a series of neurometabolic examinations in an indiscriminate manner is not indicated in evaluating MR, but can be considered in some cases of overall developmental retardation.