Brief clinical report: dup(4p15 leads to 4pter) in a 19-year-old woman resulting from a maternal 4;14 translocation

Characterization of terminal chromosome anomalies using multisubtelomere FISH

Telomeric repeat sequences (TTAGGG) are known to cap the termini of every human chromosome. Proximal to these repeat sequences are chromosome-specific repeat sequences, which in turn are distal to gene-rich regions. Submicroscopic, subtle, or cryptic abnormalities in these regions can now be investigated using commercial probe sets for all of the chromosome-specific subtelomeric regions of the human genome. Using this technology, previously unidentified genomic imbalance has been found in a proportion of patients with idiopathic developmental delay and learning difficulties. We have used these probe sets to investigate cases with apparently terminal anomalies detected on G-banded chromosome analysis. As a result of such investigations, we have found that 3 (19%) of 16 apparently terminal deletion cases were the result of more complex rearrangements involving other chromosome subtelomeres. The remaining 13 cases contained no chromosome-specific subtelomere repeats on the deleted arm, but in all 16 cases, the TTAGGG telomere repeat cap was present. A further case was investigated where extra material was found in the terminal region of the chromosome 12 short arm, found to represent a complex inversion/duplication/deletion rearrangement. Investigation of all cases with terminal anomalies, including apparently terminal deletions, is likely to uncover further cases involving complex rearrangements and should lead to a greater understanding of the mechanisms by which these abnormalities arise.

Clinical manifestations of trisomy 4p syndrome

Trisomy 4p syndrome is a distinct clinical entity which was noted almost a quarter century ago by Wilson et al. [71] and later was delineated by Gonzalez and colleagues [29]. The variation in the length of duplicated segment usually associated with monosomy of other genetic material which has resulted in confusion and as a result a so-called 4p syndrome could not be recognized without cytogenetic analysis. We wish to draw the attention of clinicians to this subject by presenting the description of over 75 cases including one from our clinic and stress the point that molecular approaches are imperative to characterize this anomaly. After extensive review, it appears that patients retaining at least the distal two-thirds to the entire short arm share an overlapping phenotypic expression that constitutes pure trisomy 4p syndrome which includes prominent glabella, bulbous nose with flat or depressed nasal bridge, retrognathia, pointed chin, short neck with low hairline, enlarged ears with abnormal helix and antihelix, rocker-bottom feet with prominent heel. Arachnodactyly and camptodactyly. Molecular characterization of 4p is imperative. We have also included an extensive bibliography for clinicians who may find it useful as a single reference source for evaluating their future cases.

CONCLUSION

The 4p-syndrome is a distinct entity but without cytogenetic evaluation, the syndrome can not be recognized.

Partial trisomy 4p resulting from a balanced intrachromosomal insertion, 4(q313p14p16)

Partial trisomy 4p was found in a child with dysmorphic features. Cytogenetic investigations in the parents revealed an intrachromosomal insertion in the mother, 46,XX,ins (4) (q313p14p16). The proband was trisomic for 4p(p14p16) as a result of a recombination event in the mother's chromosome 4 at meiosis. The clinical features of the proband are compared with those found in the literature.

Coloboma and microphthalmos in chromosomal aberrations. Chromosomal aberrations and neural crest cell developmental field

A survey of more than 500 reports on patients with autosomal chromosomal aberrations associated with microphthalmos and/or coloboma shows that these anomalies are unspecific. Anterior chamber anomalies were common as were abnormal ears, preauricular pits and tags, cleft lip-palate, micrognathia, urogenital malformations, congenital heart disease, atresia of the anus and minor malformations of the hands and feet. It is proposed that the chromosomal aberrations induce faulty development of neural crest cells and rostral neural plate derivatives.

The spectrum of clinical features in CHARGE syndrome

Fifteen patients with CHARGE syndrome are described, nine sporadic and six familial. A recognizable pattern of malformations is present which appears to constitute a syndrome rather than a non-random association. In addition to acronymic features of Coloboma, Heart disease, Atresia of the choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies, other important diagnostic features include facial paralysis and feeding problems suggestive of velopharyngeal incompetency. A square facial appearance with asymmetry and malar flattening is characteristic, and long philtrum or prominent nasal columella may be present. Characteristic external ear anomalies and a 'wedge'-shaped audiogram may be unique to this syndrome. Short stature and hypogonadism with genital hypoplasia is pituitary or possibly hypothalamic in origin. Each feature varies from normal to severe involvement including mental function, and no single feature appears to be necessary for diagnosis.

Familial Wolf's syndrome with a hidden 4p deletion by translocation of an 8p segment. Unbalanced inheritance from a maternal translocation (4;8)(p15.3;p22). Case report, review and risk estimates

This is the case report of a patient with Wolf's syndrome having a monosomy 4pter----p15.3 and an additional trisomy 8pter----p22, derived from a maternal balanced translocation t(4;8)(p15.3;p22) after 2:2 disjunction and adjacent-1 segregation. The patient's phenotype is presumably slightly modified by the trisomic 8p segment. Literature analyses indicate that phenotypic "hybrids" with traits of monosomy 4p and of other autosomal segment trisomies exist. The dermatoglyphics of the patient were not highly characteristic for Wolf's syndrome. Also the dermatoglyphics of the balanced translocation carriers were unspecific and did not reflect the carrier status. Pedigree analyses of 46 reported families with reciprocal translocations involving the short arm of chromosome 4 show a high risk (20.5% +/- 4.6%) for unbalanced offspring (trisomy or monosomy 4p) after 2:2 disjunction and adjacent-1 segregation, if the breakpoint in the recipient chromosome is terminal and the resulting imbalance concerns the 4p segment only. It is considerably lower (4.5% +/- 2.5%) if the breakpoint in the recipient chromosome is subterminal, as in the reported case, and the resulting imbalance concerns other chromosome segments additionally to the 4p segment. In both instances, the risk decreases with increasing segment length. The risk for unidentified abortions, stillbirths or neonatal deaths is also high in these families (about 40%). The frequency of progeny with balanced compared to progeny with normal karyotype corresponds to the expected 50% for alternate segregation.

Trisomy 4p in four relatives: variability and lack of distinctive features in phenotypic expression

We report two brothers and two second cousins with 4p trisomy secondary to a familial translocation t(4;7) (p12;q36). A comparison of their physical features demonstrates the variability of clinical manifestations associated with this chromosome abnormality. While previous authors have emphasized the distinctiveness of the 4p trisomy syndrome, the variability seen in the affected relatives in this family suggests that trisomy 4p is one of the less distinctive chromosomal syndromes. Further comparison of our patients with the previously reported cases of 4p trisomy and with two cases whose chromosomal breakpoints were similar confirms this variability. Studies of phenotype/karyotype correlations in affected relatives provides the best opportunity to determine the phenotypic consequences of a specific (that is, identical) translocation. Studies of unrelated persons are complicated by the effects of different breakpoints and of possible partial deletions.