title: Intrachromosomal insertion mimicking a pericentric inversion: molecular cytogenetic characterization of a three break rearrangement of chromosome 20.
abstract: 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.
authors.affiliation: Laboratoire de Cytogénétique, Groupe Hospitalier Cochin-Saint-Vincent-de-Paul, Paris, France.
authors.forename: Azarnouche
authors.initials: A
authors.lastname: Ardalan
authors.forename: Marguerite
authors.initials: M
authors.lastname: Prieur
authors.forename: Agnès
authors.initials: A
authors.lastname: Choiset
authors.forename: Catherine
authors.initials: C
authors.lastname: Turleau
authors.forename: Françoise
authors.initials: F
authors.lastname: Goutieres
authors.forename: Sylvie
authors.initials: S
authors.lastname: Girard-Orgeolet
mesh_terms: D000015:Abnormalities, Multiple / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D019457:Chromosome Breakage; D007446:Chromosome Inversion; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics*; D003456:Cryptorchidism / Q000175:diagnosis / Q000235:genetics; D003937:Diagnosis, Differential; D004827:Epilepsy / Q000175:diagnosis / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D007621:Karyotyping; D008297:Male; D008831:Microcephaly / Q000175:diagnosis / Q000235:genetics; D011995:Recombination, Genetic
chemical_list: D005819:Genetic Markers