Abstract
BackgroundChromosomal imbalances, recognized as the major cause of mental retardation, are often due to submicroscopic deletions or duplications not evidenced by conventional cytogenetic methods. To date, interstitial deletion of long arm of chromosome 2 have been reported for more than 100 cases, although studies reporting small interstitial deletions involving the 2q24.1q24.2 region are rare. With the widespread clinical use of comparative genomic hybridization chromosomal microarray technology, several cryptic chromosome imbalances have outlined new genotype-phenotype correlations and isolated a number of distinctive clinical conditions.Resultshere we report on a girl with mental retardation and generalized hypotonia. A genome-wide screen for copy number variations (CNVs) using single nucleotide polymorphisms (SNPs) array revealed a 7.5 Mb interstitial deletion of chromosome region 2q24.1q24.2 encompassing 59 genes, which was absent in parents. The gene content analysis of the deleted region and review of the literature revealed the presence of some genes that may be indicated as good candidate in generating the main clinical features of the patient.Discussionthe present case represents a further patient described in the literature with an interstitial deletion of chromosome 2q24.1q24.2. Our patient shares some clinical features with the previously reported patients carriers of overlapping 2q24 deletion. Although more cases are needed to delineate the full-blown phenotype of 2q24.1q24.2 deletion syndrome, published data and present observation suggest that hemizygosity of this region results in a clinically recognizable phenotype. Considering these clinical and cytogenetic similarities, we suggest the existence of an emerging syndrome associated to 2q24.1q24.2 region.
Highlights
Chromosomal imbalances, recognized as the major cause of mental retardation, are often due to submicroscopic deletions or duplications not evidenced by conventional cytogenetic methods
We present a case with a 7.5 Mb de novo deletion of chromosome 2q24.1q24.2 encompassing 59 genes detected by single nucleotide polymorphisms (SNPs) array
A comparison of the clinical features observed in our patient with the previously reported cases identified by array comparative genomic hybridization, that clearly overlap the current case, shows several common features including mental retardation and hypotonia
Summary
Chromosomal imbalances, recognized as the major cause of mental retardation, are often due to submicroscopic deletions or duplications not evidenced by conventional cytogenetic methods. Over 70 patients with a terminal deletion and over 30 with an interstitial deletion have already been reported [1,2]. Most of the examined patients presented a mental retardation varying between severe and profound, hypotonia and dysmorphic features. The most frequent interstitial deletion involves the cytogenetic bands 2q31q33 and corresponds to a specific phenotype [3,4]. Magri et al [6] reported a patient with severe mental retardation, muscular hypotonia and characteristic dysmorphic features, who carried a de novo 5.3 Mb deletion in 2q24.2q24.3
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