A taxonomic approach to the del(4p) phenotype

Clinical and epilepsy characteristics in Wolf-Hirschhorn syndrome (4p-): A review

Wolf-Hirschhorn syndrome (WHS) is araredisorderwithan estimated prevalence being around 1 in 50,000 births. The syndrome is caused by the deletion of a critical region (Wolf-Hirschhorn Syndrome Critical region- WHSCR) on chromosome 4p16.3. WHS is clinically characterized by pre-and postnatal growth restriction, hypotonia, intellectual disability, craniofacial dysmorphismand congenital fusion anomalies. The clinical aspects are variable due to the deletion size.Consistently, epilepsy is one of the major concerns for parents and professionals caring for children with WHS. Seizures tend to occur in over 90% of patients, with onset within the first 3 years of life, and a peak incidence at around 6-12 months of age. Approximately 20% of patients had the first seizure onset within the first 6 months of age, almost 50% at 6 to 12 months of age and about 25% later than 12 months of age. The main types of epileptic seizures occurring in patients with WHS were generalized tonic-clonic seizures (around 70%). These were followed by tonic spasms (20%); focal seizures with impaired awareness (12%) and clonicseizures in 7% of patients.Seizures are often triggered by fever, followed by infections of various systems. Particularly, half of WHS patients experience status epilepticus in the first years of life, which can be fatal. Due to limited number of reports on the topic of EEG abnormalities in epilepsy among WHS patients, it is difficult to determine whether there are any characteristic deviations for WHS. Although more than 300 persons with WHS have been reported in the literature, there is sparse knowledge about epilepsy and methods of its anti-seizure medication (ASM) management with an assessment of their effectiveness. The purpose of this systematic review is to briefly summarize achievements and advances in the field of epilepsy in Wolf-Hirschhorn syndrome.

The delineation of the Wolf-Hirschhorn syndrome over six decades: Illustration of the ongoing advances in phenotype analysis and cytogenomic technology

Since Hirschhorn's description in 1961, the history and chronology of the clinical, cytogenetic, and molecular characterization of Wolf-Hirschhorn syndrome (WHS) elegantly demonstrates the remarkable advances in genetic technology over the last six decades that have paralleled the delineation of the phenotype. After mention in the Human Chromosome Newsletter of a child with a visible deletion of the top of a B chromosome group, 4-5, Hirschhorn and colleagues companioned their report with that of Wolf et al. in Humangenetik in 1965, and the condition was recognized and named. The 1960-1970s witnessed the description of many of the now classic chromosome disorders, including WHS, while HRB allowed for the recognition of chromosome syndromes with smaller deletions/duplications. FISH probes, developed in the next two decades, enabled the characterization of the critical region of WHS and improved clinical diagnosis with subtelomeric probes. Cytogenomic microarray in the early-mid 2000s led to both improved diagnosis of WHS patients and documentation of microdeletions of <5 megabases, helping to characterize the critical regions for specific component phenotypes (e.g., seizures, face). Recently exome sequencing technology has led to the discovery of WHS patients with WHSC1 loss of function variants, displaying some cardinal features of the phenotype (face, growth, and developmental delay).

Ring chromosome 4 in a patient with early onset type 2 diabetes, deafness, and developmental delay

To date, most ring formations of chromosome 4 lose distal 4p and usually include the Wolf-Hirschhorn syndrome region [WHS]. We describe a case with r(4) in a girl who presented without features of WHS; she had mild developmental delay, deafness, short stature, obesity, and the onset of type 2 diabetes in adolescence, a distinctive phenotype. Although 4p was significantly deleted on Giemsa banding, the 4p junction was distal to the WHS and FGFR3 but proximal to the D4S3360 marker. The 4q breakpoint was close to the telomere. The phenotype appears different from previous patients with 4p- or r(4), which have had more extensive 4p deletion.

An epidemiological study of Wolf-Hirschhorn syndrome: life expectancy and cause of mortality

OBJECTIVE

Early research into Wolf-Hirschhorn syndrome (WHS) described a high mortality and no relationship between deletion size and phenotype. This may need to be revised in the light of improved cytogenetic resolution and medical care. We have collected epidemiological data to allow the calculation of birth incidence and mortality figures. In addition, we have investigated the possibility of a relationship between deletion size and mortality.

METHOD

Information relating to past and present cases diagnosed in the UK was collected by multiple ascertainment.

RESULTS

A total of 159 cases were collected. The status (alive or dead) was determined for 146, of whom 96 are alive, 37 had died, and 13 were detected on prenatal diagnostic tests. A minimum birth incidence of 1 in 95 896 was calculated. The crude infant mortality rate was 17% (23/132) and in the first two years of life the mortality rate was 21% (28/132). Cases with large de novo deletions (proximal to and including p15.2) were more likely to have died than those with smaller deletions (odds ratio=5.7, 95% CI=1.7-19.9) after adjusting for age. A comparison of survival curves for de novo deletions and translocations did not show a statistically significant difference (p=0.11). The median survival time for de novo deletions was 34+ years while for translocation cases it was 18+ years.

CONCLUSIONS

The mortality rate is lower than previously reported. There is a statistically significant relationship between deletion size and overall risk of death in de novo deletion cases. The difference in survival curves between de novo deletions and translocations is not statistically significant.

A case of insertional translocation involving chromosomes 2 and 4

We report on a 6-year-old Caucasian boy with direct insertion of genetic material from the short arm of chromosome 4 to the short arm of chromosome 2. He was referred for evaluation because of global developmental delay and seizure disorder. A karyotype performed at 4 1/2 months of age, by a laboratory elsewhere, reportedly showed a deletion of chromosome 4(p12). When we saw him, he had macrocephaly, hypotonia, psychomotor retardation, multiple minor congenital anomalies, and EEG abnormalities. Repeat chromosomes performed by our laboratory revealed that his karyotype was 46,XY,dir ins(2;4)(p24;p15.3p13). Fluorescence in situ hybridization (FISH) analysis, using chromosomes 2 and 4 painting probes confirmed that material from 4p has been translocated to 2p. Also, FISH analysis using the Wolf-Hirschhorn critical region probe revealed that both loci are intact. Parental chromosomes were normal. This complex rearrangement, though it appears balanced, probably might have resulted in either a structural loss of genetic material or functional loss of a gene action. Thus, his phenotype could be explained by this de novo insertion of chromosome 4 material into chromosome 2. There is no reported case of this specific chromosome rearrangement.

Zimmer phocomelia: delineation by principal coordinate analysis

We present a 46,XX stillborn fetus with tetraphocomelia, absence of ears, severe hypoplasia of nose, cleft palate, pulmonary hypoplasia, imperforate anus and vagina, and phallus-like structure on an otherwise undefined perineum. The pattern of abnormalities resembles the tetraphocomelic condition described by Zimmer et al. in 1985. Tetraphocomelia, ear/nose hypoplasia with facial clefts, pulmonary hypoplasia, and defects of the caudal end including imperforate anus, and abnormal genitalia constitute a distinct pattern of malformation termed Zimmer phocomelia. Principal coordinate analysis with Gower's similarity index supported the clinical impression that cases reported by Zimmer and the present case are distinct from other phocomelic conditions. Although Zimmer phocomelia is currently referred to as "X-linked amelia," documentation of a female case with a penis-like structure in this report as well as consanguinity in the original family in Zimmer's report indicates that this condition is likely inherited in an autosomal recessive fashion. Zimmer phocomelia may be a more appropriate name than X-linked amelia.

Interstitial deletions of the short arm of chromosome 4 in patients with a similar combination of multiple minor anomalies and mental retardation

Interstitial deletions of chromosome 4 have been described rarely and have had variable presentations. We describe the phenotypic characteristics associated with interstitial deletion of the p14-16 region of chromosome 4 in 7 patients with multiple minor anomalies in common, and with mental retardation. A review of published cases of interstitial deletions of the short arm of chromosome 4 is provided. These deletions present a distinct phenotype which is different from that of Wolf-Hirschhorn syndrome.

Preliminary phenotypic map of chromosome 4p16 based on 4p deletions

We have collected and analyzed clinical information from 11 patients with chromosome 4p deletions or rearrangements characterized by various molecular techniques. Comparing the extent of these patients' deletions with their respective clinical presentations led to the proposal of a preliminary phenotypic map of chromosome 4p. This map consists of regions which, when deleted, are associated with specific clinical manifestations. Nonspecific changes such as mental and growth retardation are not localized, and probably result from the deletion of more than one gene or region. The region associated with most of the facial traits considered typical in Wolf-Hirschhorn syndrome (WHS) patients coincides with the currently proposed WHS critical region (WHSCR), but some anomalies commonly seen in WHS appear to map outside of the WHSCR. The observation of clinodactyly in 2 patients with nonoverlapping deletions allows assignment of these defects to at least 2 separate regions in 4p16. These initial observations and attempts at genotype/phenotype correlation lay the groundwork for identifying the genetic basis of these malformations, a common objective of gene mapping efforts and chromosome deletion studies.

Numerical syndromology: a mathematical approach to the nosology of complex phenotypes

Numerical taxonomy is defined by Sneath and Sokal as the grouping of taxonomic units on the basis of their character states by numerical methods of multivariate data analysis, and syndromology as the study of multiple congenital anomaly (MCA) syndromes and of their nosology. We present here an application of those methods to the analysis of overlapping syndromes. The main advantage of numerical taxonomy is that it allows simultaneous objective and unweighted analysis of multiple traits, giving the possibility to test mathematically the clinical hypotheses about the heterogeneity between closely resembling syndromes and uncovering objective patterns of anomalies, to be compared with the subjective pattern recognition process which characterizes most of the diagnostic approach in syndromology. In this paper, we explored 5 syndromes whose most severe expression belongs to the cerebroacrovisceral early lethality (CAVE) phenotype: hydrolethalus, severe Smith-Lemli-Opitz, orofaciodigital type VI (Varadi-Papp), holoprosencephaly-polydactyly, and Pallister-Hall syndromes. Fifty-five published cases, including many overlapping cases, were submitted to principal factor analysis followed by hierarchical clustering and graphical scaling. Results show that the 5 syndromes clearly constitute independent phenotypic entities, that some of the original diagnoses have to be reconsidered, and that many of the overlapping cases may be unambiguously set in one category. Hypothalamic hamartoblastoma appears to be a nonspecific dysplasia occurring in any of the 5 disorders.

Syndrome of proximal interstitial deletion 4p15: report of three cases and review of the literature

We report on two boys and a girl with interstitial deletion in the short arm of chromosome 4 including the segment p15.2p15.33. All had normal growth with psychomotor retardation, multiple minor congenital anomalies, and a characteristic face distinct from that of the Wolf-Hirschhorn syndrome. One of the patients had congenitally enlarged penis. These patients resemble some of the previously reported patients with similar cytogenetic abnormalities and suggests the recognition of a specific clinical chromosome deletion syndrome.

A patient with Wolf-Hirschhorn syndrome originating from translocation t(4;8) (p16.3;q24.3)pat

We present here a 7 year old girl with the clinical signs of Wolf-Hirschhorn syndrome (WHS). Only on high resolution banding was a deletion of 4p16.3 suspected in both the proband and the father. Further studies using simultaneous R banding and FISH, with cosmid probe pc847.351 containing the mildly repetitive fragment 847-EC, confirmed the diagnosis and showed a paternal balanced translocation t(4;8)(p16.3;q24.3).

Toward the complete genomic map and molecular pathology of human chromosome 4

The identification of disease genes via molecular DNA cloning has revolutionized human genetics and medicine. Both the candidate gene approach and positional cloning have been used successfully. The defects causing Huntington's disease, facioscapulohumeral muscular dystrophy, piebaldism, Hurler/Scheie syndrome, one form of autosomal recessive retinitis pigmentosa, and a second locus for autosomal dominant polycystic kidney disease have recently been localized to chromosome 4. In addition to the rapid progress in the cloning of the 203-megabase chromosome, the presence of more than 60 closely spaced microsatellites on this chromosome will undoubtedly lead to the localization of additional disease genes. In order to consider cloned genes as potential candidates for disorders assigned to chromosome 4, it is important to collect and order all genes with respect to their chromosomal localization. Analysis of cytogenetically visible interstitial and terminal deletions should also be helpful in defining new disease gene loci and in mapping novel genes. These data represent the status quo of the integrated molecular map for chromosome 4.

Molecular characterisation of chromosome 4p deletions resulting in Wolf-Hirschhorn syndrome

We present three patients with Wolf-Hirschhorn syndrome with small cytogenetic deletions of 4p16. One case is a de novo translocation and two cases represent de novo deletions. Using molecular techniques we determined the extent of these deletions and attempted to ascertain parental origin. Case 1 had a deletion of 4p16.3 with a breakpoint proximal to D4S10, case 2 had a larger deletion including D4S62 in 4p16.2, and case 3 had the largest deletion which included D4S240, but not the Raf2 locus in 4p16.1. The parental origin of the deletion in case 3 was paternal; the other two cases were indeterminable. Our results show that these three deletions include the currently proposed Wolf-Hirschhorn syndrome critical region within the most distal 2 Mb of 4p16.3 and offer supportive evidence for continuous terminal deletions.

Epileptic seizures in the 4p- syndrome: report of two cases

We report ictal phenomena in two patients with the 4p- syndrome captured on simultaneous video-EEG monitor. One patient, diagnosed as having partial epilepsy, had complex partial seizures and hemiconvulsive status epilepticus. This was associated with more severe mental retardation. The second patient was diagnosed as having the West syndrome and exhibited tonic spasms with a cluster formation. We conclude that various types of epileptic seizures may occur in patients with the 4p- syndrome, including grand mal and myoclonic seizures.

Clinical anthropometry and medical genetics: a compilation of body measurements in genetic and congenital disorders

Anthropometry has become an important tool in the study of genetic conditions, particularly as a diagnostic aid for the clinical geneticist. However, many practicing physicians do not do anthropometry of patients for several reasons, such as: appropriate measurements in a given situation are unknown; normative reference data are unavailable; or analysis and interpretation of the data are confusing. In this review we present an annotated compilation of informative measurements for hereditary and congenital disorders and a guide to normative anthropometric data of use in evaluation and diagnosis of such disorders. Further development of multivariate approaches will enhance the application of anthropometry as a means of identifying and classifying a syndrome and documenting the natural history of many disorders. Continued cooperation among physicians, geneticists, and anthropologists for the collection and assessment of patient and normative data is essential if these goals are to be realized.