Intrachromosomal insertion mimicking a pericentric inversion: Molecular cytogenetic characterization of a three break rearrangement of chromosome 20

Intrachromosomal insertions are uncommon rearrangements, in which a chromosomal segment is intercalated into another part of the same chromosome. The insertion may occur in the same arm (paracentric) or in the other arm (pericentric). The cytogenetic recognition of these structurally rearranged chro...

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Bibliographic Details
Published in:American journal of medical genetics. Part A 2005-10, Vol.138A (3), p.288-293
Main Authors: Ardalan, Azarnouche, Prieur, Marguerite, Choiset, Agnès, Turleau, Catherine, Goutieres, Françoise, Girard‐Orgeolet, Sylvie
Format: Article
Language:English
Subjects:
Abnormalities, Multiple - diagnosis
Abnormalities, Multiple - genetics
Child
Child, Preschool
Chromosome Breakage
Chromosome Inversion
Chromosomes, Human, Pair 20 - genetics
Cryptorchidism - diagnosis
Cryptorchidism - genetics
deletion 20q
Diagnosis, Differential
Epilepsy - diagnosis
Epilepsy - genetics
Genetic Markers
Humans
In Situ Hybridization, Fluorescence
Infant
intrachromosomal insertion
inversion
Karyotyping
Male
Microcephaly - diagnosis
Microcephaly - genetics
Recombination, Genetic
trisomy 20p
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Summary:Intrachromosomal insertions are uncommon rearrangements, in which a chromosomal segment is intercalated into another part of the same chromosome. The insertion may occur in the same arm (paracentric) or in the other arm (pericentric). The cytogenetic recognition of these structurally rearranged chromosomes can be difficult, and intrachromosomal insertions can be easily mistaken for inversions. We describe a case of a familial pericentric insertion of chromosome 20, initially misdiagnosed as a pericentric inversion in the healthy carrier and then reinterpreted as insertion in an abnormal child with a recombinant chromosome. Fluorescence in situ hybridization (FISH) allowed us to confirm the mechanism of recombinant formation and to locate the three breakpoints precisely. Our cytogenetically unbalanced epileptic patient carried a 20q deletion and 20p duplication, and the genes, CHRNA4 and KCNQ2 that have been implicated in autosomal dominant epilepsy, were deleted. The haplo‐insufficiency of these two genes may contribute to the cause of epilepsy in patients with ring chromosome 20. © 2005 Wiley‐Liss, Inc.
ISSN:1552-4825
1552-4833
DOI:10.1002/ajmg.a.30966