Partial trisomy 3p in two siblings: clinical and pathological findings

Distal 3p duplication and terminal 7q deletion associated with nuchal edema and cyclopia in a fetus and a review of the literature

OBJECTIVE

To present perinatal detection of distal 3p duplication and terminal 7q deletion associated with nuchal edema and cyclopia in a fetus, and to review the literature.

MATERIALS AND METHODS

A 32-year-old, G9P0, woman who had experienced eight spontaneous abortions was found to have fetal nuchal edema, alobar holoprosencephaly, and cyclopia by prenatal ultrasound at 15 weeks of gestation. The pregnancy was subsequently terminated, and a malformed fetus was delivered with cyclopia. Molecular and conventional cytogenetic analyses were made to determine the genetic pathogenesis of fetal abnormalities.

RESULTS

The father had a karyotype of 46,XY,t(3;7)(p22.1;q36.1). The mother had a karyotype of 46,XX. The fetus had a karyotype of 46,XY,der(7)t(3;7)(p22.1;q36.1)pat. The analysis of array comparative genomic hybridization analysis revealed a 43.68-Mb duplication of 3p26.3-3p22.1 encompassing CHL1 and CNTN4, and an 8.66-Mb deletion of 7q36.1-7q36.3 encompassing SHH in the fetus.

CONCLUSION

Simultaneous occurrence of 7q deletion and 3p duplication can be associated with alobar holoprosencephaly. For the couple with a parental translocation involving 7q and 3p, prenatal ultrasound should include a detailed investigation of central nervous system anomalies.

Partial trisomy 3p and partial monosomy 11q associated with atrial septal defect, cleft palate, and developmental delay: a case report

Unbalanced translocation involving both chromosome 3p duplication and 11q deletion in the same patient is extremely rare; only 1 live-born case was reported previously. This karyotype was also detected during prenatal diagnosis of 2 different pregnancies in a Taiwanese family which were both terminated. In all 3 cases, only standard karyotyping was done to detect the abnormal karyotypes. Here, we report a 4-year-old boy with cleft palate, atrial septal defect, and hypotonia with gross and fine motor delay. Oligonucleotide-based array comparative genomic hybridization showed copy number gain from 3pter to 3p24.2 (approximately 24.5 Mb) and copy number loss from 11q25 to 11qter (approximately 5.8 Mb). This de novo unbalanced translocation event involving a terminal 3p duplication and a terminal 11q deletion provides candidate genes for further investigation of dosage effect leading to the patient's multiple phenotypic abnormalities. Genotype-phenotype correlation is difficult to make in this case due to the large number of genes involved. However, the description of such cases together with precise gene-level mapping of chromosomal breakpoints will add to further refinement of candidate genes to be investigated for terminal imbalances in 3p and 11q when more similar cases are reported.

Prenatal diagnosis of partial trisomy 3p (3p21-->pter) and partial monosomy 11q (11q23-->qter) associated with abnormal sonographic findings of holoprosencephaly, orofacial clefts, pyelectasis and a unilateral duplex renal system

Patients with partial trisomy 3p seldom present major dysmorphic features, and holoprosencephaly occurs in only 10% of the cases with partial trisomy 3p. It has been suggested that multiple genetic hits or environmental exposures are required for the clinical expression of holoprosencephaly. At 16 weeks of gestation, prenatal sonography identified a fetus with holoprosencephaly, orofacial clefts, pyelectasis, and a unilateral duplex renal system. Amniocentesis revealed the karyotype of 46,XX,der(11)t(3;11)(p21;q23)pat with partial trisomy 3p (3p21-->pter) and partial monosomy 11q (11q23-->qter). The pregnancy was subsequently terminated. Postnatally, the proband showed hypotelorism, a depressed nasal bridge, orofacial clefts and holoprosencephaly-premaxillary agenesis. The present case provides evidence that partial trisomy 3p/monosomy 11q can be a genetic cause of holoprosencephaly and del(11)(q23-->qter) is associated with a duplex renal system.

Prenatal diagnosis of terminal deletion 7q and partial trisomy 3p in fetuses with holoprosencephaly

Chromosome aberrations, mendelian mutations and exogenous agents can cause holoprosencephaly. Therefore, etiologic evaluation of holoprosencephaly is necessary for obstetricians and genetic counselors, once a prenatal diagnosis of holoprosencephaly has been made. We present four pregnancies in three women in which routine sonographic examinations led to the prenatal diagnosis of holoprosencephaly. Prenatal cytogenetic analysis and fluorescence in situ hybridization demonstrated a 46,XY,del(7)(pter-->q32:) and a 46,XY,der(2)t(2;3)(q37;p21)pat karyotype respectively in two fetuses with cyclopia, and a 46,XX,der(2)t(2;3)(q37;p21)pat and a 46,XX,der(7)t(3;7)(p23;q36) karyotype respectively in two fetuses with premaxillary agenesis. In conclusion, terminal deletion 7q and partial trisomy 3p in holoprosencephalic fetuses indicates that genes contributing to craniofacial development reside in these critical regions. Proper prognostic evaluation in further pregnancies requires expertise in cytogenetics and genetic counseling.

Molecular characterization of trisomic segment 3p24.1-->3pter: a case with review of the literature

A 1-year-old male infant was found to have a de novo unbalanced translocation, resulting in trisomy for a portion of the short arm of chromosome 3, i.e. 46,XY,der(7)t(3;7) (p24.1;p22). Previous cases with a so-called "trisomy 3p syndrome" were evaluated by GTG banding, while we attempted to characterize the present case by the FISH-technique. The major clinical features included: dysmorphic ears, decreased muscle tone and seizure episodes associated with fever, which are concordant with "trisomy 3p syndrome". The most common malformations of trisomy 3p syndrome are: psychomotor and mental retardation, short neck, hypertelorism/telecanthus and congenital heart defects. Predominantly, the 3p trisomies have been maternally derived and the major mechanism of inheritance is due to a malsegregation of the chromosomes that are involved in a parental balanced translocation. A review of 44 cases from 35 studies revealed that the clinical manifestations have been quite varied, depending upon the amount of 3p2 material in the trisomic state, but interestingly a recognizable pattern of features was obvious in those cases whose cytogenetic findings and clinical histories were known.

Autosomal imbalance syndromes: genetic interactions and the origin of congenital malformations in aneuploidy syndromes

In some autosomal imbalance syndromes an additional imbalance interferes with the occurrence of the anomalies typical of the syndrome itself. For example, polydactyly was found in patients with "pure" del(3p) more frequently (11/23) than in patients where these deletions were associated with different partial trisomies (2/28). The opposite situation was shown in del(7q) syndrome where various defects of the holoprosencephalic group were found to be rarer in patients with "pure" deletions, than in cases with simultaneous occurrence of various partial trisomies. It suggests the importance of gene interaction in determining the phenotypic picture of autosomal imbalance syndromes.

Perspectives on holoprosencephaly: Part I. Epidemiology, genetics, and syndromology

This paper provides an updated, comprehensive, critical review of the epidemiology, genetics, and syndromic aspects of holoprosencephaly and is divided into four parts. In the first part, epidemiologic aspects are discussed under the following headings: prevalence, temporal trends, socioeconomic status, exposure to environmental teratogens, maternal and paternal ages, pregnancy histories, and birth weights. The second part analyzes the facial phenotypes because the genetic and syndromic aspects of holoprosencephaly cannot be understood without knowledge of facial variability and its meaning. Topics discussed include cyclopia, ethmocephaly, cebocephaly, median cleft lip, and less severe facial dysmorphism. The third section, on genetics, analyzes associated anomalies, chromosomal and non-chromosomal holoprosencephaly, family studies, twin studies, genetics of nonsyndromic holoprosencephaly, and recurrence risks. The final section on syndromology summarizes 48 conditions in which some degree of holoprosencephaly may be a feature.

Insertional translocations: report of two new families and review of the literature

We describe two families with insertional translocations. In the first, a large family ascertained because of repeated pregnancy loss, the insertional translocation, ins(1;3)(q32;p13pter), was found to be segregating through three generations. In the second family, ascertained through a proposita with congenital malformations, multiple spontaneous abortions also occurred. The father had an insertional translocation, inv 4(p14,q21.1)ins(7,4)(q32;q21.1 q23). These cases illustrate that recurrent fetal wastage may be caused by insertional translocations and in fact may be the only clinical manifestation of this unusual type of chromosome rearrangement.

Holoprosencephaly: association with interstitial deletion of 2p and review of the cytogenetic literature

Chromosome analysis with high-resolution banding showed a small de novo interstitial deletion of chromosome 2(p21----p22.2) in an infant with holoprosencephaly. This is the first such observation. There is a well-known association with abnormalities of chromosome 13 (most commonly trisomy 13, but also dup(13q) and del(13q) and chromosome 18 (most often del(18p), but also trisomy 18). Review of the literature also showed duplications of 3p and deletions of 7q to be causes of the holoprosencephaly defect.

A de novo 3p;8p unbalanced translocation resulting in partial dup(3p) and partial del(8p)

We present the first case of a de novo translocation resulting in dup(3p). Giemsa banding studies tentatively identified the source of the extra genetic material as 3p. Clinical findings were compatible with those previously reported in dup(3p) patients, further defining this cytogenetic anomaly as a distinct, clinically identifiable syndrome.

Presumptive mosaic origin of an XX/XY female with ambiguous genitalia

A child with ambiguous genitalia had an XX/XY karyotype in all tissues examined. Analyses of 11 informative polymorphisms, both chromosomal and genetic (Rh and HLA), showed no difference between the two cell lines. It is unlikely that the child originated from fertilisation of the egg and the second polar body by two sperms; therefore, we hypothesise that the child originated from an XXY zygote after mitotic errors during cleavage. Recent findings of differences in the chromosome constitution between the extra-embryonic tissues and the fetus support this view.

Prenatal diagnosis of a dup(3p) with holoprosencephaly

The prenatal diagnosis of dup(3p) was made in a female conceptus, the father being a known carrier of a balanced translocation t(3;10)(p21;q26). Interruption of pregnancy at 19 weeks showed a fetus with a holoprosencephaly field defect. Two other cases of dup(3p) have been observed in the same family. The malformations were different in each of the 3 patients, suggesting a considerable degree of variability of dup(3p).

Partial trisomy 3p syndrome

Two cousins with an unbalanced chromosome translocation (partial trisomy 3p) are described. Both children have a clinically recognizable syndrome of square facies with prominent cheeks, narrow bitemporal regions, psychomotor retardation and congenital heart disease. Extended family studies showed one other individual proven to have partial trisomy 3p karyotype, two retarded individuals with congenital heart disease who probably had it, and 14 balanced carriers of the translocation t(1;3)(q43;p21). This report confirms the characteristic clinical appearance of affected individuals and emphasizes the frequency in which congenital heart disease is the presenting feature of partial trisomy 3p. An additional 22 cases of partial 3p trisomy are reviewed.

A complex three way translocation resulting in two sibs with partial trisomy 3p23----3pter

A male infant with multiple congenital anomalies and psychomotor retardation was found to have a translocation resulting in partial trisomy for the distal part of chromosome 3p. An older sister with similar clinical findings had an identical karyotype. Chromosome studies in the phenotypically normal parents revealed a balanced translocation in the mother involving chromosomes 3, 11, and 18. An identical translocation was found in one of the normal children.