Mosaic 13 trisomy due to de novo 13/13 translocation with subsequent fission karyotype: 46,XX,-13,+t(13;13)(p11;q11)/46,XX,del(13)(p11)

Summary A severely retarded child with multiple malformations was found to present a mosaic karyotype 46,XX,-13,+t(13;13)(p11;q11)/46,XX,del (13)(p11), which probably originated as the result of a de novo 13/13 translocation in a parental gamete, followed by postzygotic fission of the translocation chromosomse.     

Mosaic 13 trisomy due to de novo 13/13 translocation with subsequent fission. Karyotype: 46,XX,-13, +t(13;13)(p11;q11)/46,XX,del(13)(p11). A second example

In this paper we report a second example of 13 trisomy mosaicism due to de novo 13/13 translocation followed by postzygotic fission of the translocation chromosome in a polymalformed female newborn.     

46,X,i(Xq)/47,XX,+13 mosaicism

A 10-year-old girl with short stature and other features of Turner's syndrome was found to be a mosaic consisting of 46,X,i(Xq) and 47,XX,+13 cell lines, a hitherto undescribed situation. She had none of the clinical features of trisomy 13 syndrome, with a possible exception of postaxial polydactyly of the left foot. Her PHA-stimulated blood lymphocytes and EB virus-transformed B lymphocytes both revealed the Xi(Xq)/XX,+13 mosaicism, while her skin fibroblasts showed an exclusively 46,X,i(Xq) karyotype. Studies using Q-and R-banding heteromorphisms as markers indicated that the patient started as a 13 trisomic zygote resulting from a maternal meiotic error, followed by the loss of chromosome 13 at an early mitotic division. C-banding analysis revealed two C banding blocks in the iso X chromosome, an indication that the chromosome was dicentric. BrdU-Hoechst-Giemsa analysis revealed that the iso X chromosome was late-replicating with both its arms either synchronously or asynchronously replicating. The iso X chromosome was thus designated as idic (Xq)(p11:p11). In view of the presence of the XX cell line, it was concluded that the patient started as an XX,+13 zygote, followed by two mitotic events, the loss of a chromosome 13 and the formation of the iso X chromosome, occurring either simultaneously or in succession.     

Human cytogenetics: 46 chromosomes, 46 years and counting

Human cytogenetics was born in 1956 with the fundamental, but empowering, discovery that normal human cells contain 46 chromosomes. Since then, this field and our understanding of the link between chromosomal defects and disease have grown in spurts that have been fuelled by advances in cytogenetic technology. As a mature enterprise, cytogenetics now informs human genomics, disease and cancer genetics, chromosome evolution and the relationship of nuclear structure to function.     

Trisomy 13qter by tandem duplication 46, XX, dir dup 13 (q21 qter), 9qh+]

A tandem translocation of chromosome 13-46,XXdup13(q21 leads to qter)--occurred de novo in a patient with the following features: normal birthweight; early feeding difficulties; mild psychomotor retardation; low set hairline on the forehead; thick eyebrows; long, upturned eyelashes; pointed nose; micrognathia; large, flat, posteriorly rotated ears; multiple hemangiomata; normal hematological status. The hypothesis of an unequal crossing-over is discussed, as well as the possibility of constructing a phenotypic map of chromosome 13.     

Chimerism 46,XX/46,XY in a phenotypic female

Summary A female patient is reported with lymphocyte chromosome chimerism (46,XX/46,XY). Her whole-body chimerism was confirmed in the AB0 blood group system by the presence of two different erythrycyte populations, A₁0 and 00. Normal findings were recorded at physical and gynecological examination, except for mammary hypoplasia and sterility of 7 years duration, the latter complaint being the cause for genetic examination of the patient.     

46,XX/46,XX,del (10) (p13)/47,XX,+r/47,XX,del (10) (p13), + r mosaicism and partial trisomy 10p phenotype (author's transl)]

The mosaicism 46,XX/46,XX,del(10)(p13)/47,XX, +r/47,XX,del(10)(p13), +r was found in the lymphocytes and the fibroblasts of a patient with the following : profound mental retardation; craniofacial dysmorphism with frontal bossing, fine eyebrows, a large hypoplastic nasal bridge, prognathism of the upper jaw, thick lips; a long and thin neck; congenital heart disease; skeletal malformations, with club feet; and hypotonia and lax ligaments. These malformations, compatible with the trisomy 10p syndrome, suggest that the supernumerary ring chromosome was composed of 10p material. An increase of HK1 and GOT1 activities was found. This is in favour of a partial trisomy of chromosome 10. The relative frequencies of the clones constituting the mosaic vary from tissue to tissue and with time.     

Etude d'une observation de chromosome du groupe 13–15 en anneau (46,XY,15r)

Résumé Observation d'un garçon de 8 ans et demi de petite taille, microcéphalique avec retard mental mais sans dysmorphie faciale ou autre malformation. Le caryotype fait à partir de cultures de leucocytes met en évidence la présence d'un anneau remplaçant un chromosome 13–15 absent. L'autoradiographie démontre que l'anneau provient d'un N^o 15.

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A ring D chromosome (46,XY,15r)

Summary A male infant, 8 and half years old, of short stature, is microcephalic with mental retardation but no facial dysmorphy or other malformation. The caryotype in peripherical leucocyte cultures revealed a chromosome complement with a ring replacing a missing 13–15 chromosome. This ring was identified as a chromosome n^o 15 by autoradiography.

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Zusammenfassung Die Autoren berichten über einen 81/2 Jahre alten Jungen mit Kleinwuchs, Mitrocephalie und Schwachsinn. Es fand sich jedoch weder eine Dysmorphie des Gesichtes noch eine andere Mißbildung. Der Karyotyp in peripheren Leukocytenkulturen zeigte ein Ringchromosom an Stelle eines Chromosoms de Gruppe 13–15. Mit Autoradiographie ließ sich dieser Ring als Chromosom Nr. 15 identifizieren.

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Clinique des Maladies des enfants et Hygiène du premier âge (Professeur R. Jean)