[Evaluation and diagnosis of patients with genetic mental retardation: standardised clinical evaluation protocols]

Mental retardation (MR) affects approximately 2-3% of the general population and around 75% of the known causes of MR are thought to have a genetic origin. The aim of this work is to describe a standardised model of diagnostic approach to patients with mental retardation of a genetic origin (MRGO).

The clinician has to draw up a detailed case history and carry out a thorough dysmorphological physical examination that enables a reasonable differential diagnosis to be reached. The next step will be to request the complementary studies needed to confirm or reject the initial suspected diagnosis. Accurate information about the personal, prenatal (pregnancy) and perinatal (childbirth) history must also be collected. The postnatal history will also provide relevant clinical information. The familial history is a fundamental element of any genetic disease and must be gathered by drawing up the family tree or lineage. The physical and dysmorphological examination must be ordered, completed and detailed, and measurements of the somatometric parameters required to demonstrate and quantify the existence of an anomaly in any anatomical structure will also have to be made. Photos of the patient are a great aid because they allow comparison with recognisable dysmorphic syndromes. The last phase involves requesting complementary studies, including consultations with other specialists. The confirmation or exclusion of MR usually results from biochemical-metabolic, cytogenetic or molecular studies.

In cases of MRGO a good patient record accompanied by a thorough physical and dysmorphological study allow the clinical geneticist to orientate the diagnosis in the right direction and to request the specific genetic laboratory tests to confirm (or reject) its causation.