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. 2010 Feb;18(2):163-70.
doi: 10.1038/ejhg.2009.152. Epub 2009 Oct 7.

The 2q23.1 microdeletion syndrome: clinical and behavioural phenotype

Bregje W M van Bon  1 , David A Koolen, Louise Brueton, Dominic McMullan, Klaske D Lichtenbelt, Lesley C Adès, Gregory Peters, Kate Gibson, Susan Moloney, Francesca Novara, Tiziano Pramparo, Bernardo Dalla Bernardina, Leonardo Zoccante, Umberto Balottin, Fausta Piazza, Vanna Pecile, Paolo Gasparini, Veronica Guerci, Marleen Kets, Rolph Pfundt, Arjan P de Brouwer, Joris A Veltman, Nicole de Leeuw, Meredith Wilson, Jayne Antony, Santina Reitano, Daniela Luciano, Marco Fichera, Corrado Romano, Han G Brunner, Orsetta Zuffardi, Bert B A de Vries
Affiliations

The 2q23.1 microdeletion syndrome: clinical and behavioural phenotype

Bregje W M van Bon et al. Eur J Hum Genet. 2010 Feb.

Erratum in

  • Eur J Hum Genet. 2010 Feb;18(2):170. Moloney, Susan [added]
  • Eur J Hum Genet. 2010 Oct;18(10):1171

Abstract

Six submicroscopic deletions comprising chromosome band 2q23.1 in patients with severe mental retardation (MR), short stature, microcephaly and epilepsy have been reported, suggesting that haploinsufficiency of one or more genes in the 2q23.1 region might be responsible for the common phenotypic features in these patients. In this study, we report the molecular and clinical characterisation of nine new 2q23.1 deletion patients and a clinical update on two previously reported patients. All patients were mentally retarded with pronounced speech delay and additional abnormalities including short stature, seizures, microcephaly and coarse facies. The majority of cases presented with stereotypic repetitive behaviour, a disturbed sleep pattern and a broad-based gait. These features led to the initial clinical impression of Angelman, Rett or Smith-Magenis syndromes in several patients. The overlapping 2q23.1 deletion region in all 15 patients comprises only one gene, namely, MBD5. Interestingly, MBD5 is a member of the methyl CpG-binding domain protein family, which also comprises MECP2, mutated in Rett's syndrome. Another gene in the 2q23.1 region, EPC2, was deleted in 12 patients who had a broader phenotype than those with a deletion of MBD5 only. EPC2 is a member of the polycomb protein family, involved in heterochromatin formation and might be involved in causing MR. Patients with a 2q23.1 microdeletion present with a variable phenotype and the diagnosis should be considered in mentally retarded children with coarse facies, seizures, disturbed sleeping patterns and additional specific behavioural problems.

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Figures

Figure 1
Figure 1
(a) Clinical photographs of all patients, except for patient 10. Note a broad chin in patients 1, 2, 3 and 9, downturned corners of the mouth in patients 1, 2, 3, 5, 6 and 9, a full everted lower lip in patients 1, 4, 5, 7, 8a and 9, a hypotonic face in patients 2, 3, 5, 7 and 9 and a coarse facial appearance in patients 2, 4, 5, 7 and 9. (b) Overview of all 2q23.1 deletions mapped in the UCSC genome browser Hg 18 (http://genome.ucsc.edu/). The overlapping region of all deletions comprises a minimal part of the untranslated region of the brain-expressed isoform of MBD5. *The exact size of the deletion in case 2 of Jaillard et al is unknown and varies between 2.4 and 5.4 Mb, with a maximum deletion between 145.1 and 150.6 Mb. (c) Deletions in sibpair 8a and 8b include the non-coding region of the brain-expressed isoform of MBD5. The distal break point of deletions lies approximately 50 kb of the first exon of the regular isoform of MBD5.
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