Prenatal diagnosis of a de novo reciprocal translocation 46,XX,t(1;18) (p22;q23)

A case is reported in which a de novo balanced translocation 46,XX,t(l;18Xp22;q23) was diagnosed prenatally.     

Unusual segregation of t(11;22) resulting from crossing-over followed by 3:1 disjunction at meiosis I

Reciprocal translocation t(11;22)(q23;q11) is of particular interest because the unbalanced offspring of the translocation carriers usually present with a supernumerary derivative chromosome 22. This common unbalanced karyotype is the result of 3:1 chromosome segregation during meiosis. We report the third case of a rare segregation pattern of a paternal 11; 22 translocation. The proband's karyotype revealed the presence of a der(11) and two copies of a der(22), i.e. 47, XX, t(11; 22)(q23;q11), +der(22) t(11;22)pat. The karyotype is the result of paternal 3:1 segregation after crossing-over involving the derived and the normal chromosome 22, as revealed by chromosome polymorphism analysis. Contrary to the preferential maternal transmission of this common unbalanced translocation, the data from the literature, including our case, may suggest preferential paternal transmission of this rare type of unbalanced translocation.     

Melkersson-Rosenthal syndrome and de novo autosomal t(9;21)(p11;p11) translocation

In this report we describe a 26-year-old female with the typical clinical symptoms and signs of Melkersson-Rosenthal syndrome, an autosomal dominant disorder with variable expression, and a de novo t(9;21)(p11;p11), and suggest that the "Melkersson-Rosenthal gene" is located at 9p11.     

Partial trisomy 16q in two boys resulting from a maternal translocation, t(15;16) (p12;q11)

Two male infants with almost complete trisomy 16q due to a maternal translocation, are reported. The phenotypic similarities of these patients who had trisomy 16q11 leads 16qter and of the eight previously published reports of partial trisomy 16q, were compared.     

Paternal origin of the de novo constitutional t(11;22)(q23;q11)

The constitutional t(11;22)(q23;q11) is a well-known recurrent non-Robertsonian translocation in humans. Although translocations generally occur in a random fashion, the break points of t(11;22)s are concentrated within several hundred base pairs on 11q23 and 22q11. These regions are characterized by palindromic AT-rich repeats (PATRRs), which appear to be responsible for the genomic instability. Translocation-specific PCR detects de novo t(11;22)s in sperm from healthy males at a frequency of 1/10⁴–10⁵, but never in lymphoblasts, fibroblasts or other human somatic cell lines. This suggests that the generation of t(11;22) rearrangement is linked to gametogenesis, although female germ cells have not been tested. Here, we have studied eight cases of de novo t(11;22) to determine the parental origin of the translocation using the polymorphisms on the relevant PATRRs. All of the eight translocations were found to be of paternal origin. This result implicates a possible novel mechanism of sperm-specific generation of palindrome-mediated chromosomal translocations.     

Unusual mosaic karyotype resulting from adjacent 1 segregation of t(11;22): importance of performing skin fibroblast karyotype in patients with unexplained multiple congenital anomalies

We report a patient with a mosaic karyotype resulting from an adjacent 1 segregation of the familial autosomal translocation (11;22). The karyotype seen in fibroblast is 46,XY,der(22)t(11;22)(q23.3;q11.2)/46,XY. No evidence of the abnormal cell line was seen in the cultures obtained from the lymphocytes. The clinical phenotype of the patient does not fit a particular pattern of partial monosomy 22 or partial trisomy 11. There are some features that have been previously reported in patients with trisomy 11q23 --> qter. The mosaic karyotype in our patient could be a result of a series of postzygotic mitotic events of a zygote carrying the der(22) chromosome. These mechanisms involve events that are well documented for several chromosomes. This case underscores the necessity of performing exhaustive cytogenetic analysis in patients with an abnormal phenotype with a family history of a chromosome rearrangement in fibroblast cells if lymphocyte analysis is normal.     

Di George anomaly associated with a de novo Y;22 translocation resulting in monosomy del(22)(q11.2)

We report on an infant, born to a diabetic mother, who presented with hypocalcemia and congenital heart disease, presurgically diagnosed by echocardiography as truncus arteriosus type I. Cytogenetic analysis showed a 45,X,-Y,-22,+der-(Y)t(Y;22) (p11.3q11.2) chromosome abnormality with del(22)(q11.2). Parental chromosomes were normal. Autopsy showed persistent truncus arteriosus type II and thymic aplasia consistent with DiGeorge anomaly. This report adds to the existing literature demonstrating an association between DiGeorge anomaly and monosomy 22q11.     

Two cases of variant Philadelphia chromosome resulting from translocation (21;22) and (3;19;22)

Two further cases of variant Philadelphia chromosome are presented. The possible presence of a specific oncogene on the long arm of chromosome #22 is discussed.     

A retrospective CISS hybridization analysis of a case with de novo translocation t(18;22) resulting in an 18p—syndrome*

Voiculescu I, Toder R, Back E, Osswald P, Schempp W. A retrospective CISS hybridization analysis of a case with de novo translocation t(18;22) resulting in an 18p—syndrome. Clin Genet 1993: 43: 318–320. © Munksgaard, 1993 An unbalanced de novo translocation t(18;22) leading to a severely malformed liveborn girl with 18p—syndrome is described. Using the chromosomal in situ suppression (CISS) hybridization technique on 4-year-old G-banded chromosome preparations, it could be demonstrated that the translocation chromosome is composed of the long arm including the centromere of a chromosome 22 and the long arm of a chromosome 18. Consequently, the patient described here has lost the short arm including the centromere of chromosome 18. The possibility of restudying cytogen-etically unsolved cases in clinical cytogenetics using older G-banded chromosome preparations with the fluorescence in situ hybridization techniques is pointed out.     

Mosaicism for a small marker chromosome resulting from a familial Robertsonian translocation (21;22)

Here we describe a group of 14 patients carrying different X-autosome translocations and exhibiting phenotypes that demonstrate the range of alterations induced by such aberrations. All male carriers of an X-autosome translocation in our investigation group were infertile, whereas fertility in the female carriers was dependent on the position of the break-point in the X chromosome. Fertile women with translocation break-points outside of the critical region (Xq13-q26) in some cases passed on the translocation to their offspring. In balanced female carriers in our group, the normal X chromosome was usually inactivated, allowing full expression of genes on the translocated segments. In one case, disruption of the dystrophine gene in Xp21 led to the manifestation of Duchenne muscular dystrophy in a female carrier. Inactivation of the derivative X (Xt) in a balanced female carrier led to a partial monosomy of the autosome/disomy of the X chromosome and resulted in an aberrant phenotype. In unbalanced carriers, Xt is generally late-replicating/inactive, although failed spreading of inactivation to the autosomal segment often results in a partial trisomy, as evidenced by the case of an unbalanced translocation carrier in our group.     

Occurrence of a variant Philadelphia translocation, t(10;22), in de novo acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia (AMegL) in adults is a very rare subtype of acute myeloid leukemia (AML) and is characterized by a larger diversity of chromosomal abnormalities than the other subtypes, including 3q21q26 changes, aberrations of chromosomes 5 and 7, and the t(9;22)(q34;q11). We report the case of a 24-year-old patient with de novo AMegL and thrombocythemic cell count. Diagnosis was established with a bone marrow biopsy, and cytogenetics with G-banding revealed a t(10;22), which by FISH, was found to be a variant Philadelphia translocation involving chromosome 10q in all 20 metaphases analyzed. We believe that this is the first report of de novo AMegL with this chromosomal abnormality, and its possible correlation with morphology and thrombocytosis is discussed.     

Analysis of human sperm chromosome complements from a male heterozygous for a reciprocal translocation t(11;22)(q23;q11)

A reciprocal translocation between chromosomes 11 and 22 (t(11;22)(q23;q11)) is a site-specific translocation that is of particular interest because of the propensity for 3:1 segregation of the chromosomes during meiosis. There have been no published reports of chromosomally unbalanced offspring born as a result of adjacent 1 or 2 meiotic segregations in a heterozygote for this translocation. This could be explained by a meiotic mechanism which produces only 3:1 chromosomal segregations or by differential embryonic survival in which 2:2 adjacent segregations do not produce a viable pregnancy. To distinguish between these two possibilities, sperm chromosome complements from a man heterozygous for this 11;22 translocation were studied. The human sperm chromosomes were analysed after fertilization of zona pellucida-free golden hamster eggs. All possible 2:2 (alternate, adjacent 1, adjacent 2) and 3:1 segregations were observed and these segregations occurred in approximately equal frequencies. The frequency of other chromosome abnormalities, unrelated to the translocation, did not appear to be increased. These results indicate that the 11;22 translocation does not specifically cause 3:1 disjunction of chromosomes but that this segregation of chromosomes is more likely to result in a viable pregnancy.     

Structural aberrations of the long arm of chromosome no. 22: Report of a family with translocation t(11;22) (q25;q11)*

A chromosomal translocation t(11;22) (q25;q11) is described in a family. Four members, in two generations, had the same translocation but showed phenotypic variation. Case reports of chromosome aberrations involving the long arm of chromosome 22 associated with and without chronic myeloid leukemia (CML) are reviewed. It appears that the distal segment of the long arm of chromosome 22 is either translocated or deleted, resulting in congenital anomalies, presumably due to chromosome imbalance. In other instances, a specific breakpoint on 22q results in the origin of Philadelphia chromosome (Ph¹) associated with CML.     

Complete trisomy 5p owing to de novo translocation t(5;22)(q11;p11) with isochromosome 5p associated with a familial pericentric inversion of chromosome 2, inv 2(p21q11).

A boy with a de novo translocation (5;22) and isochromosome 5p associated with a pericentric inversion of chromosome 2 (p21q11) is described. The pericentric inversion was also present in the mother. The main clinical features of the 'complete trisomy 5p' syndrome were present in the proband.     

Masked Philadelphia chromosome caused by translocation (9;11;22)

In a patient with chronic myelocytic leukemia (CML), chromosome analysis revealed a translocation involving chromosomes No. 9, 11, and 22, with three break points, thus giving origin to a so-called "masked" Philadelphia chromosome (Ph1). A review of similar cases reported in the literature indicates that a masked Ph1 is very rare, that the chromosomes involved vary from case to case, and that in most cases the pattern of the rearrangement is quite different from that of two- and three-chromosome variant Ph1 translocations.     

Meiotic segregation in familial reciprocal translocation t(8q;22q)

We studied the chromosomes of a mentally retarded boy with minor anomalies and of his parents using a G-band stained high-resolution chromosome method. This documented dup (8q24.1 → 8qter) and dup(22pter → 22q11.2) in the boy due to a maternal balanced reciprocal translocation of chromosomes 8 and 22 and 3:1 disjunction during meiosis I. The karyotype of the boy is 47, XY, + der(22) (22pter → 22q11.2::8q24.1 → 8qter). The der(22) was involved in satellite associations and stained positively with AgNO₃ in mother and child. The case is compared to similar cases in the literature and the function of the small acrocentric marker chromosome during meiosis is discussed.     

Partial duplication 16p resulting from a 3:1 segregation of a maternal reciprocal translocation

We report on a male infant with a duplication 9p (pter → _q13) and duplication 16p (p13 → pter) resulting from a 3:1 meiotic disjunction of a maternal reciprocal translocation. In this case, the mode of segregation fits to the Pachytene-Diagram Model of Jalbert el al [1980]. The infant showed clinical features that have been described both in dup(16p) and in dup(9p). To our knowledge, this is the first time that this unbalanced karyotype has been reported.     

Alternate, adjacent 2 and 3:1 meiotic segregation products from a balanced t(13;18) (q12;q11) carrier

Cotton C, Cummins M, Smith A. Alternate, adjacent 2 and 3:1 meiotic segregation products from a balanced t(13: 18) (q12;q11) carrier.
Clin Genet 1993: 44: 193–195. © Munksgaard, 1993
We present a case in which alternate, adjacent 2 and 3:1 meiotic segregations have occurred in the pregnancies of a female carrier of a balanced reciprocal translocation - 46,XX,t(13;18) (q12;q11). Products of five conceptions effectively showed trisomy 18q, trisomy 18p or monosomy 18p. This is one of the rare rearrangements which can give rise to a variety of segregation modes including adjacent 2.