Isochromosome (18q) in siblings

A report is presented on a familial occurrence of isochromosome (18q) in a newborn infant and in a fetus in the 24th week of gestation after amniocentesis.     

Trisomy 18 and 18p- features in a case of isochromosome 18q [46,XY,i(18q)]: prenatal diagnosis and autopsy report

This paper reports the prenatal diagnosis and autopsy findings of a case of true isochromosome 18q [46,XY,i(18q)] with severe cephalic malformations. Comparison is made with other cases of i(18q).     

Features of trisomy 18 and 18p-syndromes in an infant with 46, XY, i(18q)

An isochromosome for the long arm of chromosome number 18 - 46,XY,i(18q) - was found in an infant who had features of both trisomy 18 and 18p- syndromes. Findings compatible with trisomy 18 included postmature delivery, prominent occiput, severe congenital heart disease, overlapping fingers, and rocker-bottom feet. Those of 18p- syndrome, which frequently resembles Turner syndrome, were downward obliquity to the palpebral fissures, short, webbed neck, low posterior hairline, and widely-spaced nipples. The infant died of heart failure at 3.5 months of age. Parental karyotypes were normal.     

Congenital cardiac defect in a patient with mosaic 45,X/46,XX,i(21q) karyotype

A baby is described with 45,X/46,XX,i(21q) mosaicism. DNA analysis indicated that the abnormality arose from two independent postzygotic mutations in a 46,XX zygote, involving the paternal chromosomes 21 and X. In agreement with previous reports, most of the clinical dysmorphisms observed were consistent with Down syndrome. Moreover, congenital heart disease consisted of an atrioventricular canal associated with slight hypoplasia of the left ventricle and a mitral anulus, a complex defect including features found in both Down and Turner syndromes.     

Novel isodicentric chromosome 18 in an abnormal infant with a mosaic karyotype [46, XY/46,XY, –18,+ dic(18)(q12.2)]

A previously unreported isodicentric chromosome 18 was discovered in an abnormal infant boy whose mosaic karyotype was 46, XY/46,XY,–18, + idic(18)(q12.2). His constellation of congenital anomalies was typical of the 18q-syndrome. The clinical and cytogentic characteristics of this patient are reported, and the literature concerning isochromosomes of 18 is reviewed.     

Isochromosome 18q in a girl with holoprosencephaly,DiGeorge anomaly,and streak ovaries

We report on the clinical and pathologic findings in a girl with isochromosome 18q (46, XX,i(18q)) who had combined manifestations of monosomy 18p and trisomy 18q. Major congenital anomalies included premaxillary agenesis, alobar holoprosenphaly, double Outlet right ventricle, DiGeorge anomaly and streak ovaries. The clinical spectrum in i(18q) is very broad. © 1993 Wiley-Liss, Inc.     

Trisomy (18q) and tetrasomy (18p) resulting from isochromosome formation

In this paper we report two clinically recognizable chromosomal syndromes, both resulting from isochromosome 18 formation, i.e. trisomy 18q and tetrasomy 18p. The possible mechanisms of the isochromosome formation are discussed and the literature on subject is reviewed.     

Three cell line mosaicism involving structural and numerical abnormalities of chromosome 18 in a 3.5‐Year‐old girl: 47,XX,+18/47,XX,+del(18)(q22)/46,XX

We report on a 3.5‐year‐old girl with a mosaic karyotype including full trisomy 18, normal cells and a majority of cells with partial trisomy involving an extra chromosome 18 deleted at band q22. She had cardiac and CNS anomalies, dysmorphic facial features failure to thrive and developmental delay. A gastrostomy tube was placed at 2 years of age. The combination of improved nutrition and optimal developmental therapy has led to her sitting supported, attempting to stand and enhancement of her cognitive and non‐verbal communication abilities. Molecular investigation of the patient and her parents using microsatellite analysis has led to the conclusion that, as expected, the additional copy of chromosome 18 constituting the full trisomic cell line is maternal meiosis I in origin. The data, however, indicate that in the trisomic cell line containing the deleted chromosome 18q, the structurally abnormal 18 was of paternal origin. We think this case is the first described with both structural and numerical trisomic mosaicism involving chromosome 18 in a liveborn infant. We propose a mechanism of origin and review the literature, comparing the clinical presentation of this case with individuals having full or partial trisomy 18. © 2001 Wiley‐Liss, Inc.     

Isochromosome 18p in a mother and her child

We present a familial case of isochromosome 18p [i(18p)] as a supernumerary chromosome. The mother, who is a mosaic for i(18p) with partial tetrasomy 18p syndrome, transmitted the isochromosome to her only child. The child has the full syndrome of tetrasomy 18p. This is the first case of mosaicism i(18p) in an adult patient with clinical manifestations. © 1993 Wiley-Liss, Inc.     

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.     

A rare case of mosaic Down syndrome 46,XY/46,XY, -21, +i(21q)

Detailed studies were carried out on a patient with a rare type of mosaicism which gave rise to an effective 21 trisomy. The clinical signs of Down syndrome were minimal. The cytogenetic interpretation is that the abnormal clone had an isochromosome derived from a maternal No. 21. The normal cell line appears to be replacing the abnormal clone.     

A pseudoisochromosome 18q and an isodicentric chromosome 18

A case of pseudoisochromosome 18q of prezygotic origin and a case of isodicentric chromosome 18 of postzygotic origin are presented to validate the differentiation between a true isochromosome and a pseudoisochromosome. This differentiation may be useful in elucidating the mechanism of the origin of an isochromosome.     

Holoprosencephaly in a newborn girl with 46,XX,i(18q)

We report on a newborn girl with holoprosencephaly, microcephaly, absent right radius, and other anomalies with an 46,XX,i(18q) chromosome constitution. This is the first report of an i(18q) in syndromal alobar holoprosencephaly.     

Maternal translocation t(13:18)(q34:q11) and Edwar''s syndrome in a fetus: 47, XY, t(13:18)(q34:q11) + 18

A 32-year-old woman, who presented with four spontaneous abortions, was found to have a balanced translocation: 46,XX,t(13:18)(q34:q11). In the last pregnancy an amniocentesis was done. Abnormal constitution of the fetus had been detected: 47,XY,t(13:18)(q34:q11) + 18, and an abortion was induced. Examination of the fetal tissue confirmed the finding. The fetus showed the characteristics of Edward's syndrome. Through the patient's pedigree it was discovered that balanced translocation appeared in three generations.     

A case report of 46, XX, del (21)(q22) de novo deletion associated with Imerslund-Grasbeck syndrome

We describe a 2-year-old female patient who had megaloblastic anaemia caused by selective vitamin B₁₂ malabsorption (Imerslund-Grasbeck syndrome) and del (21)(q22). To our knowledge, this is the first observation of Imerslund-Grasbeck syndrome associated with del(21)(q22) in the literature.     

A case of de novo i(12p) with 12q whole-arm translocation mosaicism

We report a dup(12p) due to a de novo i(12p) in a girl with mosaicism for 12q whole-arm translocations onto 7p, 7q, and 11q terminal regions. The dup(12p) syndrome was confirmed by clinical, cytogenetic, and LDH-dosage studies.     

A mildly retarded woman with 46,XX/47,XX,+18 mosaicism

We describe a mildly retarded woman with trisomy 18 mosaicism. The phenotype did not suggest trisomy 18, but the mild mental retardation, asymmetric face with bushy eyebrows and thick lips, short stature, and older maternal age raised the suspicion of a chromosomal cause for her condition.     

Partial 18q trisomy and 18p monosomy resulting from a maternal pericentric inversion,inv(18)(p11.2q21.3)

A 7-year-old boy with dysmorphic features was found to have a recombinant chromosome 18, rec(18), resulting from meiotic recombination of a maternal pericentric inversion, inv(18) (p11.2q21.3), as defined by high-resolution banding. He was trisomic for the long arm (q21.3-qter) and monosomic for the short arm (p11.2-pter) of chromosome 18. His clinical features were compared with those in other rec(18) cases, and also those in monosomy 18p, trisomy 18qter and full trisomy 18 syndromes. The risk of recombinant formation for inv(18) carriers was also discussed.