A lethal presentation of de novo deletion 7q

Combined deletion of two Condensin II system genes (NCAPG2 and MCPH1) in a case of severe microcephaly and mental deficiency

7qter deletion syndrome includes prenatal and/or postnatal growth retardation, microcephaly, psychomotor delay or mental retardation and a characteristic dysmorphism. If clinical features are well described, the molecular mechanisms underlying the 7qter deletion syndrome remain unknown. Those deletions usually arise de novo. Here, we describe a young boy with an abnormal phenotype consistent with a 7qter deletion syndrome. High resolution genomic analysis (Affymetrix Human Genome Wide SNP 6.0) revealed a 7q36.3 deletion encompassing NCAPG2, ESYT2, WDR60 and VIPR2, inherited from his asymptomatic father and paternal grandfather. In addition, the patient also harbored a MCPH1 deletion inherited from his healthy mother. Combined NCAPG2 and MCPH1 deletions were correlated with low mRNA levels and protein expression in the patient. MCPH1 and NCAPG2 proteins interaction is known to control chromosome structure and we thus propose that double heterozygosity for null mutations of those two genes of the Condensin II system contribute to mental deficiency with severe microcephaly phenotype.

A case of partial 14q- with facial features of holoprosencephaly and hydranencephaly

We report a rare case of facial features of holoprosencephaly associated with hydranencephaly, with a de novo proximal interstitial deletion of the long arm of chromosome 14, specifically, del(14)(q13q21). She was born at 37 weeks of gestation and transferred to our institution at 3 years of age. The patient had midline facial anomalies consisting of cleft palate, defective nasal septum, and hypotelorism, together with endocrine abnormalities such as diabetes insipidus and hypothyroidism. Cranial computed tomography revealed the near-total loss of all cerebral tissue, with a frontal part of the cerebral falx lacking. None of the few reports of holoprosencephaly with 14q- chromosomal abnormality describe holoprosencephaly in association with hydranencephaly. The partial deletion of chromosome 14, del(14)(q13q21), may underlie the association of facial features of holoprosencephaly and hydranencephaly.

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.

De novo terminal deletion of chromosome 7 [46,XX,del(7)(q35)]

OBJECTIVE

To report a new case of de novo 7q deletion distal to q35.

METHODOLOGY

Developmental, cytogenetic and audiological investigations were carried out in the assessment of this rare chromosomal condition.

RESULTS

Moderate developmental delay, mild congenital microcephaly, growth retardation and conductive hearing impairment were found for this case of 46,XX,del(7)(q35).

CONCLUSIONS

The phenotype of 7q terminal deletion is highly variable.

Ectrodactyly and proximal/intermediate interstitial deletion 7q

We report on an individual with severe mental retardation, seizures, microcephaly, unusual face, scoliosis, and cleft feet and cleft right hand. The chromosomal study showed a proximal interstitial deletion 7q (q11.23q22). From our review of the literature, 11 patients have been reported with ectrodactyly (split hand/split foot malformation) and proximal/intermediate interstitial deletions or rearrangements of 7q. The critical segment for ectrodactyly seems to be located between 7q21.2 and 7q22.1. This malformation is present in 41% of the patients whose deletion involves the critical segment.

Partial monosomy of 7q32 in a case of de novo rcp(7;15)(q32;q15)

A de novo apparently balanced translocation between chromosomes 7 and 15 with breakpoints in q32 and q15 respectively is reported in a female child. Clinical features included general growth and psychomotor retardation, feeding problems, microcephaly, low set ears, a short neck, and brachydactyly. These findings suggested possible physical or functional partial monosomy of the 7q32 or 15q15 segments. The phenotype of this case is similar to other cases of 7q deletion.

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.

Terminal deletion of 7q presenting in utero with a truncus arteriosus and nonimmune hydrops

Terminal deletion of 7q presents with variable anatomical and developmental findings. This case is the first reported in utero diagnosis based on cytogenetic findings and in utero demonstration of resolving congestive heart failure due to a truncus arteriosus.

Holoprosencephaly and sacral agenesis in a fetus with a terminal deletion 7q36-->7qter

We describe here a fetus with holoprosencephaly and signs of caudal deficiency sequence. Chromosome examination showed a de novo balanced reciprocal translocation (7;22) (q36;q11) with loss of the derivative chromosome 22 in 50% of the cells examined. The present report and available published data indicate that the terminal region of the long arm of chromosome 7 contains genes implicated in the development of the central nervous system and the caudal region.

The interstitial deletion of bands q33-35 of long arm of chromosome 7: a review with a new case report

Interstitial or terminal deletion resulting in partial monosomy of various segments of the long arm of chromosome 7 was first recorded over two decades ago. Since then, a number of reports have correlated the severity of clinical manifestations with the length of the deletion involved. However, difficulty remains in defining a so-called "distinct syndrome". We present a new case with the shortest interstitial deletion of the long arm of chromosome 7 bands q33-35, i.e. 46,XX,del(7)(pter----q33::q35----qter). A 4-year-old black female was referred for cytogenetic evaluation due to neurodevelopmental delay. Pertinent physical examination at birth was cleft lip and cleft palate which required corrective surgery. At 2 years of age, a myringotomy tube was inserted for repeated ear infection and a hearing aid was required for conductive deafness. Neurological examination revealed poor eye contact, and severe mental and motor retardation. We reviewed 21 cases of a partial interstitial deletion of varied segments of the long arm of chromosome 7, but we were unable to establish a definite relationship with the deletion of various 7q segments with any specific clinical manifestations.

Familial holoprosencephaly associated with a translocation breakpoint at chromosomal position 7q36

A familial balanced t(7;9) (q36;q34) was reported recently. Analysis of the craniofacial features of 3 of the sibs showed signs of holoprosencephaly. Two of the sibs have an unbalanced derivative chromosome leading to del(7) (q36) and dup(9) (q34), while the other has a cytogenetically balanced translocation. These findings, together with several reports associating holoprosencephaly with terminal 7q deletions, indicate that a putative locus for holoprosencephaly resides at or near 7q36. It should now be feasible to clone this locus.

Holoprosencephaly: examples of clinical variability and etiologic heterogeneity

Clinical variability and causal heterogeneity of holoprosencephaly is discussed in relation to several newborn infants with cyclopia (cases 4,5,6), cebocephaly (cases 2,3), and premaxillary agenesis (case 1). In subjects with holoprosencephaly, the presence of multiple malformations is an indicator of concomitant chromosome aberrations, as in present case 1 (Down syndrome) and case 3 (trisomy 13). Cases 5 and 6 are two monozygotic twins with the same type of cyclopia and alobar holoprosencephaly recognized by prenatal ultrasonography. The diagnostic importance of ultrasonographic, cytogenetic, and pathological studies is pointed out in view of etiologic evaluation, genetic counseling, and prevention of holoprosencephaly.

Terminal deletions of the long arm of chromosome 7: five new cases

Twenty-two cases of terminal deletions of the long arm of chromosome 7 have been reported. We present 5 new cases, 3 of which were ascertained due to fetal holoprosencephaly, one due to anencephaly, and one due to multiple structural defects in a 15-year-old boy. The presence of holoprosencephaly in 3 of the 5 cases reported herein and in 2 previously reported cases suggests that this manifestation may be commonly observed in individuals with deletion 7q.

Chromosome 7 abnormalities in parents of children with holoprosencephaly and hydronephrosis

At least nine cases of holoprosencephaly (HPE) found in patients with confirmed loss of 7q34----7qter or 7q36----7qter have been reported in the literature. In the present report, balanced rearrangements involving chromosome 7q [inv(7)(p22.1q34) and t(4;7)(q31;q36)] were shown in two mothers examined after the birth of their non-karyotyped infants with HPE and hydronephrosis. In both cases, del(7q) was the most probable imbalance. The available data confirm the association between HPE and del(7q). Predominance of cyclopia and cebocephaly, the severest forms of HPE, suggests that del(7q) may be an important factor in arresting prosencephalon development at the earliest stages.

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.

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.