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Mosaic 18q21.2 deletions including the TCF4 gene: A clinical report
Author(s) -
Rossi Massimiliano,
Labalme Audrey,
Cordier MariePierre,
Till Marianne,
Blanchard Gaëlle,
Dubois Remi,
Guibaud Laurent,
Heissat Sophie,
Javouhey Etienne,
Lachaux Alain,
Mure PierreYves,
Ville Dorothée,
Edery Patrick,
Sanlaville Damien
Publication year - 2012
Publication title -
american journal of medical genetics part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.064
H-Index - 112
eISSN - 1552-4833
pISSN - 1552-4825
DOI - 10.1002/ajmg.a.35588
Subject(s) - haploinsufficiency , mosaic , phenotype , biology , point mutation , genetics , gene , mutation , genotype , comparative genomic hybridization , chromosome , archaeology , history
Pitt–Hopkins syndrome (PTHS) is characterized by distinctive facial dysmorphism, profound intellectual disability, and the possible occurrence of epilepsy and breathing anomalies. It is caused by haploinsufficiency of the TCF4 gene. No significant difference in clinical severity has been reported to date between PTHS patients carrying 18q21 deletions including the TCF4 gene, and those harboring TCF4 point mutations, suggesting a lack of genotype/phenotype correlation. Moreover, the size of 18q21 deletions including the TCF4 gene does not appear to have a significant effect on the phenotypic severity, suggesting that TCF4 haploinsufficiency is the most important prognostic factor in 18q deletions. We describe two unrelated patients presenting with clinical features reminiscent of PTHS and carrying mosaic interstitial 18q21 deletions characterized by array comparative genomic hybridization. One of the patients presented the lowest level of mosaic 18q21 deletion reported to date (5–10%). Our report and a review of the literature show that the mosaic status does not appear to have a significant effect on the clinical severity of 18q21 deletions, which are associated with a poor neurological outcome, whereas a mosaic TCF4 point mutation can result in a significantly milder phenotype. Malformations of internal organs are currently considered to be rare in PTHS. The patients described here had visceral anomalies, suggesting that a full morphological assessment, including heart and abdominal ultrasound scans, should be performed systematically in PTHS patients. © 2012 Wiley Periodicals, Inc.