A male infant with monosomy 21.

A male infant with total monosomy 21 identified by Q-, G- and R-banding is described. His main symptoms are hypertonia, micrognathia, microphthalmus, imperforate anus, ambiguous external genitalia, floating and malopposed thumbs, overlying fingers, right clubfoot and growth retardation. Both parents are phenotypically as well as karotypically normal.     

Partial trisomy and monosomy 21 in an infant with an unusual de novo 21/21 translocation

A 3-month-old boy with a 46,XY,--21,+t(21;21)(pter leads to q22.3::q22.3 leads to q11::p11 leads to pter) karyotype, implicating trisomy for the 21q11 leads to 21q22.2 segment and monosomy for the 21q22.3 sub-band, is described. Most of the clinical features corresponded to Down syndrome ; other signs such as large ears, prominent nasal bridge and retromicrognathia were interpreted as the expression of 21q22.3 monosomy. The abnormal monocentric chromosome had satellites and stalks on both ends as a result of a 21q;21q translocation followed by deletion of one centromere region. Despite similar stalk size and NOR-Ag positiveness a significantly higher association frequency of the centrometric end as compared to the acentric end was found. This observation suggests that the satellite association phenomenon is not exclusively NOR-dependent, but that the centromeric and/or p11 regions of acrocentrics also play an important role.     

A low frequency mosaicism for monosomy 21 in a live born female

Summary Monosomy 21, whether homogeneous or as a mosaicism, is very uncommon. We report here a 3-month-old white female with a low degree of monosomy 21 in the blood karyotype (6.5%, 110 cells counted) but not in the skin fibroblasts, which contained only the normal chromosome complement.The patient's physical features included microcephaly with frontal slanting; prominent occiput; ridge-shaped sutures; agenesis of the corpus callosum; large, prominent ears; high and narrow palate; micrognathia; tetralogy of Fallot; crowded toes; and dry, thick skin with very little subcutaneous tissue. The case is discussed in light of the suggested clinical features of the monosomy 21 syndrome and the possible implications of such a low-grade mosaicism in prenatal diagnosis.     

A case of monosomy 21

A new case of monosomy 21 was observed in a newborn male. Characteristic clinical features include: an antimongoloid eye slants, large and low set ears, flat nose bridge, hypoplastic nipples, cardiac anomalies, muscular hypotonia, retarded psychomotor development. The karyotypes of the parents were normal.     

Ring chromosome 21. Observation in a female infant

A case of a female infant with karyotype 46,XX,r(21)/45,XX,-21 is reported. From comparison of the phenotypic anomalies with the other similar cases the large variability of the 21q- syndrome is evident.     

18q部分单体患儿的细胞和分子遗传学研究

临床发现1例智力低下伴轻度发育迟缓的女性患儿,对患儿进行G显带高分辨染色体核型分析, 发现18q21→qter缺失, 经多色荧光原位杂交和双色荧光原位杂交证实, 确定其核型为46,XX,del(18)(pter→q21:),ish del(18)(D18Z1+, qter-)。用DNA多态性方法分析, 该患儿从18q22.1至18qter区域内至少有8.7 Mbp丢失, 有MBP基因和GALNR基因缺失。缺失的18号染色体源自父亲。患者的智力低下和生长发育迟缓是18q21→qter缺失的结果, 或许与MBP基因和GALNR基因的缺失有关。     

X monosomy and 21 trisomy in a sibship

Summary The case of a sibship of 4, 2 members of which present aneuploïdy (45,X and 47,XX,21+) is reported. The paternal grandfather and grandmother are first cousins and there is a large number of centromeric associations in the father.     

X monosomy and 21 trisomy in a sibship.

The case of a sibship of 4, 2 members of which present aneuplo?dy (45,X and 47,XX,21+) is reported. The paternal grandfather and grandmother are first cousins and there is a large number of centromeric associations in the father.     

Partial monosomy 13 and 21 due to a familial 13/21 translocation

Summary Two patients are described with a monosomy for the proximal part of the long arm of chromosome 13 and for the distal part of the long arm of chromosome 21, due to an unbalanced 13/21 translocation.     

A rare case of monosomy 18p: translocation between chromosomes 18 and 21

A rare case of monosomy 18p with molecular cytogenetic characterization of 18;21 whole arm translocation is presented. An 8-year-old gril with mental deficiency and growth deficiency was the child of a 45-year-old healthy mother and 50-year-old nonconsanguineous father with unremarkable prenatal history. She had a round face, flat nasal bridge, micrognathia and hypotonia. Cytogenetic studies revealed de novo 45,XX,del(18)t(18;21) karyotype, which was confirmed by fluorescence in situ hybridization (FISH).     

Clonal monosomy of chromosome 21 in a case of myelodysplastic syndrome

This study reports on a cytogenetic finding in a bone marrow examination of a 47-year-old male patient treated in the Hematology and Blood Transfusion Service of the Hospital de Base in S?o José do Rio Preto, S?o Paulo State, Brazil. The only alteration found at diagnosis of myelodysplastic syndrome (MDS) subtype refractory anemia with excess blasts (RAEB-2) was clonal monosomy of chromosome 21. The patient evolved to acute myeloid leukemia type M2 and died nine months after diagnosis. Clonal monosomy of chromosome 21, as the only cytogenetic abnormality in MDS, has only been reported three times previously. This uncommon cytogenetic abnormality in MDS has been associated with a poor clinical course, although more data will be needed to determine if this prognosis is invariable.     

De novo unbalanced t(11q;21q) leading to a partial monosomy 21pter-q22.2 and 11q24-qter in a patient initially diagnosed as monosomy 21

We describe a patient in whom full monosomy 21 was initially assumed from routine GTG banded karyotyping. Re-examination with chromosome painting demonstrated an unbalanced translocation between the long arms of chromosomes 11 and 21. Fluorescence in situ hybridization (FISH) and microsatellite marker analysis revealed partial monosomy of chromosome 21 (pter-q22.2) and 11 (q24-qter). The patient was prematurely born in the 31st week of gestation and expired 3 days after delivery. She showed multiple minor anomalies, a complex cardio-vascular malformation, intestinal malrotation and cerebellar hypoplasia.     

Microphthalmia with linear skin defects syndrome in a mosaic female infant with monosomy for the Xp22 region: molecular analysis of the Xp22 breakpoint and the X-inactivation pattern

This paper describes a female infant with microphthalmia with linear skin defects syndrome (MLS) and monosomy for the Xp22 region. Her clinical features included right microphthalmia and sclerocornea, left corneal opacity, linear red rash and scar-like skin lesion on the nose and cheeks, and absence of the corpus callosum. Cytogenetic studies revealed a 45,X[18]/46,X,r(X)(p22q21) [24]/46,X,del(X)(p22)[58] karyotype. Fluorescence in situ hybridization analysis showed that the ring X chromosome was positive for DXZ1 and XIST and negative for the Xp and Xq telomeric regions, whereas the deleted X chromosome was positive for DXZ1, XIST, and the Xq telomeric region and negative for the Xp telomeric region. Microsatellite analysis for 19 loci at the X-differential region of Xp22 disclosed monosomy for Xp22 involving the critical region for the MLS gene, with the breakpoint between DXS1053 and DXS418. X-inactivation analysis for the methylation status of the PGK gene indicated the presence of inactive normal X chromosomes. The Xp22 deletion of our patient is the largest in MLS patients with molecularly defined Xp22 monosomy. Nevertheless, the result of X-inactivation analysis implies that the normal X chromosomes in the 46,X,del(X)(p22) cell lineage were more or less subject to X-inactivation, because normal X chromosomes in the 45,X and 46,X,r(X)(p22q21) cell lineages are unlikely to undergo X-inactivation. This supports the notion that functional absence of the MLS gene caused by inactivation of the normal X chromosome plays a pivotal role in the development of MLS in patients with Xp22 monosomy. Received: 16 December 1997 / Accepted: 25 February 1998     

Down and Turner syndromes in a female infant with 47,X,del(X)(p11),+21

Summary This report describes a female infant with a 47,X,del(X)(p11),+21 karyotype who has clinical features of both Down and Turner syndromes. The majority of her clinical features are suggestive of Down syndrome.     

Complete monosomy mosaic of chromosome 21: Case report and review of literature

Complete monosomy mosaic of chromosome 21 is a rare disorder. The syndromic features are highly variable. This study describes a girl of Mexican origin with complete monosomy 21 in mosaicism with novel findings, including cortical atrophy, macrostomia, pectum excavatum and immune deficiencies. Parental karyotypes were normal. FISH analysis with probes from 21q22.1–q22.2 region and centromere of X DNA probe was performed on peripheral blood lymphocytes whereas 21q22.1–q22.2 and 21q, 4p, 4q subtelomeric DNA probes were tested in fibroblasts. We propose that the monosomy 21 mosaicism is the cause of the survival of children with more than 4 months of age.