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Am J Med Genet A. 2010 Aug;152A(8):2034-8. doi: 10.1002/ajmg.a.33483.

Partial hexasomy for the Prader-Willi-Angelman syndrome critical region due to a maternally inherited large supernumerary marker chromosome.

Author information

1
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA. hoppmanchaney.nicole@mayo.edu

Abstract

Extra copies of the Prader-Willi-Angelman syndrome critical region (PWASCR) have been shown to have detrimental phenotypic effects depending on the parent of origin. Hexasomy for the PWASCR is rare; only 6 cases have been described to date. We report on a 15-year-old girl referred for developmental delay and seizures with a mosaic tricentric small marker chromosome (SMC) 15 identified by routine G-banding chromosome studies. C-banding and FISH confirmed the presence of three chromosome 15 centromeres as well as four copies of the PWASCR on the SMC in approximately 60% of interphase cells. Microsatellite genotyping documented maternal inheritance of the SMC, and methylation-sensitive multiplex ligation-dependent PCR amplification (MS-MLPA) showed that the extra copies of the PWASCR contained on the marker chromosome bear a methylation pattern similar to a normal maternal chromosome, implying maternal inheritance. These findings are consistent with the patient's phenotype as paternal inheritance of such a marker chromosome is thought to be benign. However, this patient's phenotype is the mildest described to date and may be a result of mosaicism for the SMC.

PMID:
20602489
DOI:
10.1002/ajmg.a.33483
[Indexed for MEDLINE]

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