Reaching an accurate diagnosis in children with mental retardation associated or not with dysmorphic signs is important to make precise diagnosis of a syndrome and for genetic counseling. A female case with severe growth and development delay, dysmorphic features and feeding disorder is presented. Antenataly, the fetus was observed to have increased nuchal translucency and a slight hypoplastic cerebellum. A standard karyotype was normal. RES and a submicroscopic unbalanced subtelomeric translocation t(2p; 10q) were demonstrated after birth. We show that within the framework of a collaborative approach, a concerted research of submicroscopic subtelomeric rearrangements should be performed in case of mental retardation associated with facial dysmorphic features, and when other etiologies or non-genetic factors (iatrogenic, toxic, infectious, metabolic...) have been ruled out.