A 400 kb duplication, 2.4 Mb triplication and 130 kb duplication of 9q34.3 in a patient with severe mental retardation

The presence of a duplication as well as a triplication in one chromosome is a rare rearrangement and not easy to distinguish with routine chromosomal analysis. Recent developments in array technologies, however, not only allow screening of the whole genome at a higher resolution, but also make it possible to characterize complex chromosomal rearrangements in more detail. Here we report a molecular cytogenetic analysis of a 16-year old female with severe mental retardation and an abnormality at the end of the long arm of chromosome 9. Subtelomeric multiplex ligation-dependent probe amplification (MLPA) analysis revealed that the extra material originated from the telomeric end of chromosome 9q. Fine mapping using a high-resolution single nucleotide polymorphism (SNP) array detected a duplication of similar to 400 kb upstream of a similar to 2.4 Mb triplication followed by a duplication of similar to 130 kb of chromosome 9q34.3. This study underscores the value of combining conventional karyotyping with novel array technologies to unravel complex chromosomal alterations in order to study their phenotypic impact. (c) 2008 Elsevier Masson SAS. All rights reserved.