Delineation of a 2q deletion in a girl with dysmorphic features and epilepsy.

In recent years, the spectrum of available methods for the characterization of chromosomal aberrations has significantly increased. Micro-array technologies now allow the rapid fine mapping of small genomic imbalances. Here we used various technologies to characterize a de novo translocation t(2;15) in a girl with dysmorphic features, severe developmental delay and frequent seizures. Multiplex-FISH (M-FISH) excluded the involvement of other chromosomes than chromosomes 2 and 15. We used an oligonucleotide array containing more than 10.000 SNPs, that is, the GeneChip Mapping 10K 2.0 SNP Affymetrix array, and readily fine-mapped a deletion in chromosomal region 2q24.1 --> 2q31.1. The extent of this deletion was verified with multicolor BAC-clone hybridizations. The deletion has a size of about 13 Mb and is within a gene rich region containing about 76 genes. Interestingly, several of these genes are ion channel genes or genes involved in neuron differentiation, so that the frequently occurring seizures are probably due to loss or haploinsufficiency of one or more of these genes.