Partial deletion of the short arm of chromosome 3 (3p25----3pter). Further delineation of the clinical phenotype

3p deletion syndrome: implications for cochlear implantation

OBJECTIVE AND IMPORTANCE

To describe the role of cochlear implantation in patients with 3p deletion syndrome. Additionally, this paper will review non-mastoid approaches to the cochlea potentially used in cases of mastoid abnormalities.

CLINICAL PRESENTATION

A 23-month-old child with 3p deletion syndrome (3pDS) presented with suspected hearing loss and characteristic craniofacial abnormalities. Bilateral sensorineural hearing loss (SNHL) was confirmed. Temporal bone computed tomography showed poorly developed mastoids bilaterally.

INTERVENTION

Cochlear implantation was successfully undertaken using a retro-auricular transmeatal approach.

CONCLUSION

SNHL is commonly encountered in patients with 3pDS and can be improved by cochlear implantation. In this patient population, particular attention must be given to pre-operative imaging and possible altered mastoid anatomy may exist. In doing so, intra-operative complications can be avoided.

Molecular cytogenetic characterization of a subtle interstitial del(3)(p25.3p26.2) in a patient with deletion 3p syndrome

Deletion 3p syndrome is associated with characteristic facial features, growth failure, and mental retardation. Typically, individuals with deletion 3p syndrome have terminal deletions that result in loss of material from 3p25 to 3pter. We present a child with a clinical phenotype consistent with deletion 3p syndrome (ptosis, microcephaly, growth retardation, and developmental delay) and a subtle interstitial deletion in the distal portion of the short arm of chromosome 3, del(3)(p25.3p26.2). Fluorescence in situ hybridization (FISH) studies using 3p subtelomeric probes confirmed the terminal region of chromosome 3 was present. Sequence tagged sites (STS)-linked BAC clones mapping to chromosomal region 3p25-p26 were used to characterize the interstitial deletion by FISH. The results indicate the deletion is within a region of approximately 4.5 Mb between STS markers D3S3630 and D3S1304. This interstitial deletion lies within all previously reported terminal deletions in deletion 3p syndrome individuals, and represents the smallest reported deletion associated with deletion 3p syndrome. Characterization of the deletion may help identify genes important to growth and development that contribute to the deletion 3p syndrome phenotype when present in a hemizygous state.

Chromosomal abnormalities and epilepsy: a review for clinicians and gene hunters

PURPOSE

We analyzed databases on chromosomal anomalies and epilepsy to identify chromosomal regions where abnormalities are associated with clinically recognizable epilepsy syndromes. The expectation was that these regions could then be offered as targets in the search for epilepsy genes.

METHODS

The cytogenetic program of the Oxford Medical Database, and the PubMed database were used to identify chromosomal aberrations associated with seizures and/or EEG abnormalities. The literature on selected small anomalies thus identified was reviewed from a clinical and electroencephalographic viewpoint, to classify the seizures and syndromes according to the current International League Against Epilepsy (ILAE) classification.

RESULTS

There were 400 different chromosomal imbalances described with seizures or EEG abnormalities. Eight chromosomal disorders had a high association with epilepsy. These comprised: the Wolf-Hirschhorn (4p-) syndrome, Miller-Dieker syndrome (del 17p13.3), Angelman syndrome (del 15q11-q13), the inversion duplication 15 syndrome, terminal deletions of chromosome 1q and 1p, and ring chromosomes 14 and 20. Many other segments had a weaker association with seizures. The poor quality of description of the epileptology in many reports thwarted an attempt to make precise karyotype-phenotype correlations.

CONCLUSIONS

We identified certain chromosomal regions where aberrations had an evident association with seizures, and these regions may be useful targets for gene hunters. New correlations with specific epilepsy syndromes were not revealed. Clinicians should continue to search for small chromosomal abnormalities associated with specific epilepsy syndromes that could provide important clues for finding epilepsy genes, and the epileptology should be rigorously characterized.

A terminal deletion of the short arm of chromosome 3: karyotype 46, XY, del (3) (p25-pter); a case report and literature review

We describe a boy with a deletion of the short arm of chromosome 3; (46, XY, del (3) (p25-pter) who presented several minor craniofacial anomalies at birth. Only 34 cases of small distal 3p deletion have been described in the literature, seven of them showed hearing loss and four of the 34 cases had brain anomalies. But in none of the 34 cases the middle and internal ear were radiographically examined. Despite the severe hearing loss detected by auditory brainstem evoked responses (ABR), computerized tomographic scanning (CT-scan) of the ear showed a normal anatomy in this patient. The head CT-scan and magnetic resonance imaging (MRI) disclosed a hypoplastic corpus callosum and an enlargement of the lateral ventricles.

Precise localisation of 3p25 breakpoints in four patients with the 3p-syndrome

In patients with the 3p-syndrome, hemizygous deletion of 3p25-pter is associated with profound growth failure, characteristic facial features, and mental retardation. We performed a molecular genetic analysis of 3p25 breakpoints in four patients with the 3p- syndrome, and a fifth patient with a more complex abnormality, 46,XY,der(3)t(3;?)(p25.3;?). EBV transformed lymphoblasts from each of the patients were initially characterised using fluorescent in situ hybridisation (FISH) and polymorphic microsatellite analyses. The 3p-chromosome from each patient was isolated from the normal chromosome 3 in somatic cell hybrid lines and subsequently analysed with polymorphic and monomorphic PCR amplifiable markers from 3p25. The analysis clearly shows that all five breakpoints are distinct. Furthermore, we have identified yeast artificial chromosomes that cross the 3p25 breakpoints of all four 3p-patients. Two of the patients were deleted for the von Hippel-Lindau (VHL) tumour suppressor gene, although neither has yet developed evidence of VHL disease. The patient with the most centromeric breakpoint, between D3S1585 and D3S1263, had the most severe clinical phenotype including an endocardial cushion defect that was not observed in any of the four patients who had more telomeric breakpoints. This study should provide useful insights into critical regions within 3p25 that are involved in normal human growth and development.

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.

Infant with del(3) (p25-pter): karyotype-phenotype correlation and review of previously reported cases

We describe a boy with monosomy for the distal part of the short arm of chromosome 3. He had a congenital heart defect, tetramelic hexadactyly, and typical craniofacial anomalies. Comparison with previously reported cases confirms that the phenotype consists of an identifiable pattern of malformation.

Terminal deletion of the short arm of chromosome 3

A boy with growth and mental retardation, flat occiput, high and broad forehead, blepharoptosis, narrow palpebral fissures, low set, malformed ears, short neck, anal atresia, deep sacral dimple is reported. High-resolution banding analysis showed terminal deletion of the short arm of chromosome 3 (46,XY,del(3)(p25.3)). Deletions of the short arm of chromosome 3 are relatively rare. The clinical features of the patient are compared with those of 19 previously reported cases.

Mother and son with deletion of 3p25-pter

We report on a mother and son with a 3p25-pter deletion. Both have postnatal growth retardation, mental retardation, apparently low-set or malformed ears, and telecanthus. The mother also has ptosis and multiple joint pains, while the son has a long philtrum and anteverted nares. These phenotypes are compared to those of other 3p- patients. Both patients have many manifestations previously described. The son appears to be more severely affected than the mother.

Loss of the 3p25.3 band is critical in the manifestation of del(3p) syndrome: karyotype-phenotype correlation in cases with deficiency of the distal portion of the short arm of chromosome 3

Two patients with monosomy for the distal portion of the short arm of chromosome 3 are described. Chromosome analysis on prometaphase cells demonstrated a karyotype of 46,XX,del(3) (p25.3) in one patient and 46,XX,r(3)(p26.1q29) in the other. The former patient showed characteristic clinical manifestations of the 3p- syndrome, including growth failure, mental retardation, microcephaly with a flat occiput, triangular face, synophrys, blepharoptosis, hypertelorism, broad and flat nose, long philtrum, down-turned mouth, micrognathia, apparently lowset and malformed ears, fingers abnormalities, and deafness. The latter patient had a nonspecific phenotype with mental retardation, growth failure and microcephaly. Karyotype-phenotype comparisons in the present cases and 16 previously reported cases with deficiency of the distal portion of 3p suggests that deficiency of the 3p25.3 band is critical to produce the main clinical manifestations of the del(3p) syndrome.

Two infants with del(3)(p25pter) and a review of previously reported cases

Del(3)(p25pter) is associated with a characteristic multiple congenital anomalies/mental retardation syndrome. Early recognition of these manifestations and identification of the chromosome defect are essential for proper management and counseling.

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.

Partial deletion of the short arm of chromosome 3: further delineation of the 3p25-3pter syndrome

A male newborn with partial deletion of the short arm of chromosome 3 is described. The patient shares most of the features with the previously reported cases. In addition, cardiac, skeletal and gastrointestinal anomalies not previously reported are described. These characteristics may help in further delineation of the syndrome.