Ring chromosome 15: characterization by array CGH |
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Authors: | Ian A Glass Katherine A Rauen Emily Chen Jillian Parkes Donna G Alberston Daniel Pinkel Philip D Cotter |
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Institution: | (1) Department of Pediatrics, University of Washington, M2-9, 4800 Sand Point Way NE, Seattle, WA 98105, USA;(2) Division of Medical Genetics, Department of Pediatrics, University of California San Francisco, San Francisco, CA, USA;(3) Department of Genetics, Kaiser Permanente Medical Center, Oakland, CA, USA;(4) Queensland Clinical Genetics Service, Brisbane, QLD, Australia;(5) Department of Laboratory Medicine, University of California San Francisco, San Francisco, CA, USA;(6) Division of Medical Genetics, Department of Pathology, Children’s Hospital and Research Center at Oakland, 747 Fifty Second Street, Oakland, CA, USA |
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Abstract: | Ring chromosome 15 r(15)] is an uncommon finding with less than 50 patients reported. Precise genotype–phenotype correlations
are problematic because of the difficulties in determining the extent of euchromatic loss, the level of mosaicism, and the
influence of the timing of ascertainment. We report two discordant examples of r(15) patients. In the first case, prenatal
diagnosis of a de novo r(15) was made during the second trimester: mos 46,XX,r(15)(p11.2q26)32]/45,XX,-1513]/47,XX,r(15)(p11.2q26)x23]/46,XX,dic
r(15)(p11.2q26p11.2q261]/46,XX2]. Postnatal follow-up revealed extremely small stature, heart defects, and developmental
delay. Patient 2 was a 31-year-old short-statured female who was living independently: 46,XX,r(15)(p11q26). Both cases showed
loss of the 15q subtelomeric region by fluorescence in situ hybridization (FISH). To investigate the discordance in phenotypes
between the two patients, we undertook array comparative genomic hybridization (array CGH) analyses to more fully characterize
the deletions associated with these otherwise structurally indistinguishable r(15) chromosomes from conventional cytogenetic
analyses and fluorescence in situ hybridization (FISH) studies. By array CGH, patient 1 showed deletion of multiple contiguous
clones predicting an approximately 6 Mb deletion of distal 15q. In contrast, patient 2 showed loss of just the 15q subtelomeric
clone and an interstitial clone by array CGH confirming that the severity of the phenotype correlated with the size of the
deletion at the molecular level. These cases illustrate the utility of array CGH characterization for determining the size
of the associated deletion in ring chromosomes and for facilitating phenotype–genotype correlations. |
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Keywords: | Chromosome 15 Genotype– phenotype correlation Ring chromosome Postnatal phenotype Prenatal diagnosis Array CGH |
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