Ring chromosome 21 in the mother and 21/21 translocation in the fetus: karyotype: 45,XX,-21,-21,+t(21;21)(p11;q11)

In 1984 we reported a ring chromosome 21 in a normal woman with recurrent fetal wastage (Kleczkowska and Fryns, 1984). A 46,XY normal fetal karyotype was found after prenatal diagnosis at 14 1/2 weeks in a third pregnancy of this woman. In the present paper we report the prenatal diagnosis of a 21/21 translocation in a female fetus from her fourth pregnancy.     

新生儿缺氧性脑病伴46,XX,-21,+t(21;21)罕见核型一例

Abstract:This report describes a cytogenetic aberration in one neonatal patient with hypoxic-ischemic encephalopathy.A rare karyotype,46,XX,-21,+t(21;21), was detected.This de nono chromosomal abnormality may be caused by the meiotic non-disjunction of chromosomes during gametogenesis along with the formation of Robertsonian translocation between homologous chromosome 21.     

Down syndrome in two siblings with 47,XY,+21 and 46,XY/46,XY,-21,+t(21q;21q)

Summary This is the first report in the literature of siblings affected with Down syndrome; one sibling had a nondisjunction of chromosome 21 and the other a (21q;21q) translocation.     

Partial trisomy 21 (21q21 - 21q22.2)]

An abnormal chromosome 21 is reported in a child with a phenotype strongly reminiscent of trisomy 21 syndrome. It is shown to result from duplication of the segment 21q21 leads to 21q22.2. Comparison of the phenotype with that of other partial and total trisomics shows that the characteristic features of the trisomy 21 syndrome (mongolism), the mental retardation in particular - is due to trisomy 21q22.2 and perhaps 21q22.2.     

A child with a 21-ring chromosome, 45,XX,21-/46,XX,21r investigated with the banding technique

Summary Chromosomal analysis of lymphocytes and fibroblasts in a slightly retarded 7-month-old female infant with some minor malformations showed a mosaicism 45,XX,G-/46,XX,Gr. The ring chromosome was identified as No. 21 by banding technique.

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Zusammenfassung Chromosomenuntersuchungen an Lymphocyten und Fibroblasten bei einem 7 Monate alten Mädchen mit leichter statomotorischer Entwicklungsverzögerung und degenerativen Stigmata zeigten ein Mosaik 45,XX,G-/46,XX,Gr. Durch die Bandentechnik mit Trypsinbehandlung konnte das Ringchromosom als Nr.21 identifiziert werden.