Pure segmental trisomy 1q42-qter in a boy with a severe phenotype

More than 100 cases of partial trisomy 1q have been reported so far and hotspot breakpoints have been localized in q25, q32 and q42. A common clinical phenotype for trisomy 1 has included mental retardation, cranial abnormalities, highly arched palate, hypertelorism, malformation of the ears and of the toes, associated with various malformations (ocular, cardiac, urinary, gastrointestinal) whose frequency was found higher in cases with a larger trisomic imbalance. We report the clinical, cytogenetic and molecular characterization of a case of pure de novo trisomy 1q42qter with typical dysmorphisms, psychomotor retardation, dilated cerebral ventricles, ocular, cardiac and genitourinary complications. By comparing the present and the published pure 1q42qter cases with those with larger imbalances, the analysis of the genotype/phenotype of the 1q trisomy supports the segmental theory of the syndrome and confirms a constant and rather specific phenotype.