INTRODUCTION Smith-Magenis syndrome (SMS) is a well defined contiguous gene syndrome that is caused by an interstitial deletion in the 17p11.2 region. It is characterised by the presentation of characteristic facial features, brachydactylia, short stature, varying degrees of mental retardation, occasional neuropathy and a specific behavioural phenotype that points to this entity. Aims. Our aim was to report the cases of two children with SMS and carry out an approximation towards their characteristic behavioural phenotype. CASE REPORTS. We studied the cases of two 12-year-old children who were suspected of suffering from SMS following the findings of a physical exploration and the presence of a specific behavioural phenotype. This was confirmed by the genetic-molecular study which proved the existence of the 17p11.2 deletion. Conclusions. Although SMS is a relatively infrequent syndrome, a patient with mental retardation and characteristic dysmorphic features who presents an especially relevant behavioural disorder including different stereotypic movements, aggression phenomena and sleep disorders is suggestive of this diagnostic possibility.

Introducción El síndrome de Smith-Magenis (SSM) es un síndrome de genes contiguos bien definido, causado por una deleción intersticial en la región 17p11.2, que se caracteriza por presentar rasgos faciales característicos, braquidactilia, talla baja, grados variables de retraso mental, neuropatía ocasional y un fenotipo conductual específico sugerente de esta entidad.

Objetivo Presentar dos niños con SSM y realizar una aproximación a su característico fenotipo conductual.

Casos clínicos Dos niños de 12 años de edad, en los que los hallazgos en la exploración física y la presencia de un fenotipo conductual específico sugirieron la posibilidad de un SSM, hecho que se confirmó mediante la demostración de la deleción 17p11.2 en el estudio geneticomolecular.

Conclusiones Aunque el SSM es un síndrome relativamente infrecuente, la presencia en un paciente con retraso mental y rasgos dismórficos característicos, de un trastorno conductual especialmente relevante, que incluye distintas estereotipias, fenómenos de agresividad y trastornos del sueño, sugiere esta posibilidad diagnóstica.