1. Romero-Rubio MT, Andres-Celma M, Castello-Pomares ML, Rosello M, Ferrer-Bolufer I, Martinez-Castellano F. {{[ARX mutations and mental retardation of unknown etiology: three new cases in Spain.]}}. {Rev Neurol};2008 (Dec 16-31);47(12):634-637.Mutaciones en el gen ARX y retraso mental no filiado: tres nuevos casos en Espana.

INTRODUCTION. Mental retardation has an approximated prevalence of 2% in the general population and its most frequent cause is X-fragile syndrome. This genetic disorder predominantly affects males and it is mainly caused by the expansion of CGG in FMR1 gene. Recently has been demonstrated that mutations in a new called ARX gene (aristaless-related homeobox) can also cause a similar form of X linked mental retardation, as well as other neurological disorders (autism, Partington or West syndrome). The most frequent mutation that has been reported is the c.428_451 dup24, which comprises almost 60% of all described. It causes an expansion of a polyalanine tract of ARX protein. CASE REPORTS. We report three cases of mental retardation in two different families where the mutation in ARX gene c.428_451 dup24 was found while X-fragile syndrome screening was made. Personal and familiar history, phenotype and evolution are described. CONCLUSION. The molecular analysis of this mutation should be considered as a routine for the genetic diagnosis of mental retardation in males of nondrafted cause.