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Phenotypic findings due to trisomy 7p15.3-pter including the TWIST locus

P Stankiewicz1, H Thiele, C Baldermann

  • 1Institute of Human Genetics and Medical Biology, University Halle-Wittenberg, Halle/S, Germany. pawels@bcm.tmc.edu

American Journal of Medical Genetics
|September 20, 2001
PubMed

Insights

A rare genetic translocation caused partial trisomy 7p in a male infant, leading to severe developmental delays and distinct physical abnormalities. This case highlights the TWIST gene

Area of Science:

  • Genetics
  • Developmental Biology
  • Pediatrics

Background:

  • Genetic translocations can lead to unbalanced chromosomal abnormalities, resulting in partial trisomies or monosomies.
  • Partial trisomy 7p is a rare condition associated with a range of developmental and physical anomalies.

Observation:

  • A three-month-old male infant presented with growth deficiency, microcephaly, wide cranial sutures, hypertelorism, choanal stenosis, micrognathia, bilateral cryptorchidism, hypospadias, and severe developmental delay.
  • Karyotype analysis revealed a de novo unbalanced translocation: 46,XY,der(Y)t(Y;7)(p11.32;p15.3).
  • Fluorescence in situ hybridization (FISH) confirmed partial trisomy 7p, with a 7p15.3-pter fragment translocated onto the Y chromosome (Yp) near the telomere.

Findings:

  • The translocation resulted in partial trisomy of the 7p chromosome segment.
  • Molecular probes identified the breakpoint on chromosome 7 within the TWIST gene region (7p15.3-p21.1).
  • The translocated 7p fragment was found near the Yp telomere, within the pseudoautosomal region (PAR).

Implications:

  • This case suggests a potential role for the TWIST gene in abnormal skull development, particularly concerning fontanel closure.
  • Dosage effects of the TWIST gene due to trisomy 7p may contribute to the observed craniofacial abnormalities.
  • Understanding such unbalanced translocations is crucial for diagnosing and managing rare genetic disorders and their associated phenotypes.

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