Familial Wolf-Hirschhorn syndrome resulting from a cryptic translocation: a clinical and molecular study

Diagnosis of familial Wolf-Hirschhorn syndrome due to a paternal cryptic chromosomal rearrangement by conventional and molecular cytogenetic techniques

The use of conventional cytogenetic techniques in combination with fluorescent in situ hybridization (FISH) and single-nucleotide polymorphism (SNP) microarrays is necessary for the identification of cryptic rearrangements in the diagnosis of chromosomal syndromes. We report two siblings, a boy of 9 years and 9 months of age and his 7-years- and 5-month-old sister, with the classic Wolf-Hirschhorn syndrome (WHS) phenotype. Using high-resolution GTG- and NOR-banding karyotypes, as well as FISH analysis, we characterized a pure 4p deletion in both sibs and a balanced rearrangement in their father, consisting in an insertion of 4p material within a nucleolar organizing region of chromosome 15. Copy number variant (CNV) analysis using SNP arrays showed that both siblings have a similar size of 4p deletion (~6.5 Mb). Our results strongly support the need for conventional cytogenetic and FISH analysis, as well as high-density microarray mapping for the optimal characterization of the genetic imbalance in patients with WHS; parents must always be studied for recognizing cryptic balanced chromosomal rearrangements for an adequate genetic counseling.

Overlapping phenotype of Wolf-Hirschhorn and Beckwith-Wiedemann syndromes in a girl with der(4)t(4;11)(pter;pter)

We report on an 8-month-old girl with a novel unbalanced chromosomal rearrangement, consisting of a terminal deletion of 4p and a paternal duplication of terminal 11p. Each of these is associated with the well-known clinical phenotypes of Wolf-Hirschhorn syndrome (WHS) and Beckwith-Wiedemann syndrome (BWS), respectively. She presented for clinical evaluation of dysmorphic facial features, developmental delay, atrial septal defect (ASD), and left hydronephrosis. High-resolution cytogenetic analysis revealed a normal female karyotype, but subtelomeric fluorescence in situ hybridization (FISH) analysis revealed a der(4)t(4;11)(pter;pter). Both FISH and microarray CGH studies clearly demonstrated that the WHS critical regions 1 and 2 were deleted, and that the BWS imprinted domains (ID) 1 and 2 were duplicated on the der(4). Parental chromosome analysis revealed that the father carried a cryptic balanced t(4;11)(pter;pter). As expected, our patient manifests findings of both WHS (a growth retardation syndrome) and BWS (an overgrowth syndrome). We compare her unique phenotypic features with those that have been reported for both syndromes.

Mother to son amplification of a small subtelomeric deletion: A new mechanism of familial recurrence in microdeletion syndromes

A 2.8-Mb 4p16.3 terminal deletion, with proximal breakpoint at locus D4S182, was diagnosed by FISH in a 16-year-old boy who presented with a typical Wolf-Hirschhorn syndrome (WHS) phenotype. The deletion, which was maternally derived, was isolated, and a balanced translocation was ruled out in both parents by FISH with probe 33c6 (locus D4S43) falling within the patient's deletion interval, at a distance of about 2.3 Mb from the telomere. His older brother, who died from pneumonia at the age of 18 years, also presented with clinical signs consistent with WHS, including typical facial appearance and major malformations, but the genetic test was not performed. A smaller 4p deletion, spanning the 1.5 Mb region from locus D4S96 to the telomere was detected in the healthy mother. When critically analyzed, after the FISH results, she was noted to present with partial WHS facial "gestalt," borderline mental delay, a few episodes of seizures as a child, normal weight and head circumference, and height at the lower limit of normal range. This report highlights a previously undescribed mechanism of familial recurrence of a microdeletion syndrome. Potential meiotic amplification is to be considered for different subtelomeric deletions that are currently interpreted as population polymorphisms. At the same time, the present report adds new insights to mapping some peculiar WHS clinical signs, such as seizures and severe growth delay.

Molecular and genomic characterisation of cryptic chromosomal alterations leading to paternal duplication of the 11p15.5 Beckwith-Wiedemann region

BACKGROUND

Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder with increased risk of paediatric tumours. The aetiology involves epigenetic and genetic alterations affecting the 11p15 region, methylation of the differentially methylated DMR2 region being the most common defect, while less frequent aetiologies include mosaic paternal 11p uniparental disomy (11patUPD), maternally inherited mutations of the CDKN1C gene, and hypermethylation of DMR1. A few patients have cytogenetic abnormalities involving 11p15.5.

METHODS

Screening of 70 trios of BWS probands for 11p mosaic paternal UPD and for cryptic cytogenetic rearrangements using microsatellite segregation analysis identified a profile compatible with paternal 11p15 duplication in two patients.

RESULTS

Fluorescence in situ hybridisation analysis revealed in one case the unbalanced translocation der(21)t(11;21)(p15.4;q22.3) originated from missegregation of a cryptic paternal balanced translocation. The second patient, trisomic for D11S1318, carried a small de novo dup(11)(p15.5p15.5), resulting from unequal recombination at paternal meiosis I. The duplicated region involves only IC1 and spares IC2/LIT1, as shown by fluorescent in situ hybridisation (FISH) mapping of the proximal duplication breakpoint within the amino-terminal part of KvLQT1.

CONCLUSIONS

An additional patient with Wolf-Hirschorn syndrome was shown by FISH studies to carry a der(4)t(4;11)(p16.3;p15.4), contributed by a balanced translocation father. Interestingly, refined breakpoint mapping on 11p and the critical regions on the partner 21q and 4p chromosomal regions suggested that both translocations affecting 11p15.4 are mediated by segmental duplications. These findings of chromosomal rearrangements affecting 11p15.5-15.4 provide a tool to further dissect the genomics of the BWS region and the pathogenesis of this imprinting disorder.

Seizure and EEG patterns in Wolf-Hirschhorn (4p-) syndrome

Wolf-Hirschhorn syndrome (WHS) is a well-characterized chromosomal disorder that occurs due to partial deletion of the short arm of chromosome 4 (4p-). Although, about 300 cases have been reported to date, limited data are available on electroclinical findings. Information given to parents at the time of diagnosis tends to be skewed to the extreme negative. To delineate the natural history of seizures and EEG patterns in WHS, and obtain better information on diagnosis or outcome in a clinical setting, we reviewed the available literature on electroclinical findings of WHS. 4p- syndrome is characterized by distinctive seizure and EEG patterns that facilitate the early diagnosis and management of such patients.

Cutaneous T-cell lymphoma in a 21-year-old male with Wolf-Hirschhorn syndrome

We describe a case of cutaneous T-cell lymphoma occurring in a 21-year-old male with Wolf-Hirschhorn syndrome (WHS) due to a chromosome 4p16.3 deletion. This is the first documented case report of malignancy occurring in an adult with WHS. We also review the literature regarding patients with WHS and the joint occurrence of malignancy and discuss genetic changes involving chromosome 4 which may have contributed to the genesis of our patient's lymphoma.

Malignant hematological disorders in children with Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) is a rare chromosomal disorder attributable to a deletion at the short arm of chromosome 4. This syndrome is associated with characteristic facial appearance, multiple congenital abnormalities, mental retardation, feeding difficulties and failure to thrive. We report two girls with WHS who developed myelodysplastic syndrome (MDS). According to the "Category, Cytology, Cytogenetic (CCC)"classification of childhood MDS, patient 1 had refractory cytopenia with ring sideroblasts at the age of 6 years, while patient 2 had refractory cytopenia with dysplasia at the age of 5-1/2 years. Patient 1 progressed to refractory cytopenia with excess blasts within a year, while patient 2 progressed to acute lymphoblastic leukemia within 1 month of presentation. It is possible that allelic loss of a tumor suppressor gene such as WHSC1 and/or FGFR3 from the deleted segment 4p16.3 plays a critical role in the process of malignant transformation. To our knowledge, this is the first report of severe hematological complications like MDS and leukemia in children with WHS and may be an important genetic model for understanding malignant hematological transformation. This report also underscores the importance of evaluating children with WHS for hematopoietic dysfunction.

Familial cryptic translocation with del 4q34-->qter and dup 12pter-->p13 in sibs with tracheal stenosis: clinical, classical and molecular cytogenetic studies and CGH analyses from archival placental tissues evidencing tertiary trisomy 4 in one abortion specimen

We report on two retarded half-sibs of different sex and seemingly normal karyotype who had the same syndrome of minor anomalies, heart defect and a distal tracheal stenosis, and who shared a healthy mother. These findings raised suspicions of a cryptic chromosome translocation. A translocation t(4;12)(q34;p13), balanced in the mother and unbalanced in the sibs with loss of terminal 4q and gain of terminal 12p regions, was verified by FISH using whole chromosome painting, subtelomeric and YAC probes. Clinical features could be explained by partial monosomy 4q and partial trisomy 12p. Tracheal stenosis was interpreted as a consequence of the same developmental disturbance leading to esophageal atresia and tracheo-esophageal fistula. It was attributed to the 4q deletion in which esophageal atresia as also respiratory difficulties and airway obstructions had been described. Paraffin-embedded placental tissues were available from three of the five abortions of the mother allowing DNA extraction and comparative genome hybridization (CGH). Two of the abortion specimens had the same der(4)t(4;12)(q34;p13) unbalanced translocation as identified in the sibs. In the third abortion specimen, suspicious of triploidy because of partial hydatidiform mole, CGH uncovered a tertiary trisomy 4 resulting from a 3:1 segregation of the translocation chromosomes and their homologs during maternal meiosis I. Differences in CGH results using DNA generated directly or after DOP-PCR were explained by DNA fragmentation in paraffin-embedded tissues and unequal amplification. Am. J. Med. Genet. 94:271-280, 2000.

Screening for submicroscopic chromosome rearrangements in children with idiopathic mental retardation using microsatellite markers for the chromosome telomeres

Recently much attention has been given to the detection of submicroscopic chromosome rearrangements in patients with idiopathic mental retardation. We have screened 27 subjects with mental retardation and dysmorphic features for such rearrangements using a genetic marker panel screening. The screening was a pilot project using markers from the subtelomeric regions of all 41 chromosome arms. The markers were informative for monosomy in both parents at 3661902 loci (40.6%, 95% confidence interval 37.0-44.2%) in the 22 families where DNA was available from both parents. In two of the 27 subjects, submicroscopic chromosomal aberrations were detected. The first patient had a 5-6 Mb deletion of chromosome 18q and the second patient had a 4 Mb deletion of chromosome 1p. The identification of two deletions in 27 cases gave an aberration frequency of 7.5% without adjustment for marker informativeness (95% confidence interval 1-24%) and an estimated frequency of 18% if marker informativeness for monosomy was taken into account. This frequency is higher than previous estimates of the number of subtelomeric chromosome abnormalities in children with idiopathic mental retardation (5-10%) although the confidence interval is overlapping. Our study suggests that in spite of the low informativeness of this pilot screening, submicroscopic chromosome aberrations may be a common cause of dysmorphic features and mental retardation.

Natural history of Wolf-Hirschhorn syndrome: experience with 15 cases

Wolf-Hirschhorn syndrome (WHS) is a well-known chromosomal disorder attributable to partial deletion of the short arm of chromosome 4 (4p-). Although about 120 cases have been reported so far, there is still very little data on its natural history. Information given to parents at the time of diagnosis tends to be skewed to the extreme negative. To help delineate more thoroughly the natural history of WHS, and to obtain better information to answer parents' questions in a clinical setting, we evaluated 15 patients (12 females, 3 males) in three centers with the 4p- syndrome. Four of the cases had a follow-up spanning 16 years. Thirteen cases were detected by standard cytogenetics (regular G-banding 10, high-resolution banding 3), while the remaining 2 required fluorescence in situ hybridization. A total of 5/15 (33.3%) had heart lesions; 7/15 (46. 6%) had oral facial clefts; 13/15 (86.6%) had a seizure disorder, that tended to disappear with age; and 100% had severe/profound developmental retardation. One Italian patient had sensorineural deafness and 1 Utah patient had a right split hand defect. Of note, 2 Utah patients were able to walk with support (at 4 and 12 years of age, respectively), whereas 3 Italian patients and 1 Utah patient were able to walk unassisted (at 4, 5, 5 years 9 months, and 7 years of age, respectively). Two of the 3 Italian patients also achieved sphincter control (by day). The 8 patients receiving serial electroencephalogram studies showed fairly distinctive abnormalities, usually outlasting seizures. A slow, but constant progress in development was observed in all cases, during the follow-up period. In conclusion, the combined cases of the three centers represent considerable experience, providing new information on several aspects of this important deletion syndrome.

An unbalanced half-cryptic translocation involving the 6q subtelomeric region and 2p25.3 in a child with mental retardation: uses and limitations of fluorescence in situ hybridization

We report on a 5-year-old boy with minor anomalies, growth retardation, and developmental delay carrying an extra chromatin material on the terminal band of the long arm of chromosome 6. To determine the origin of this extra material, whole chromosome fluorescence in situ hybridization (FISH) was used initially. Results showed fully painted 6qs, excluding the possibility of a derivative. However, maternal cytogenetic investigation suggested the presence of a possible half-cryptic balanced translocation that was further assessed using specific subtelomeric FISH probes of chromosome 6. Results showed that the 6q subtelomeric region was translocated on an A-group chromosome that was ultimately characterized, using FISH, as chromosome 2. This illustrates the use of specific subtelomeric regions and the limitations of whole chromosome FISH to identify the origin of a subtle chromosomal abnormality.

A new strategy for cryptic telomeric translocation screening in patients with idiopathic mental retardation

Cryptic unbalanced chromosome rearrangements in the telomeric bands of human chromosomes constitute a significant cause of "idiopathic" mental retardation. Here, we have described a new strategy based upon comparative genomic hybridisation (CGH) to screen for these abnormalities. A modified CGH analysis showed three unbalanced cryptic rearrangements in five patients from three families. These chromosome abnormalities and their balanced forms in the relatives were then confirmed by fluorescence in situ hybridisation (FISH). This study describes a new approach to the diagnosis of cryptic translocations between the G band negative ends of chromosomes and confirms the significant contribution of cryptic telomeric rearrangements to idiopathic mental retardation.

Translocations involving 4p16.3 in three families: deletion causing the Pitt-Rogers-Danks syndrome and duplication resulting in a new overgrowth syndrome

Three families are reported who have a translocation involving 4p16.3. Nine subjects are described with the clinical features of the Pitt-Rogers-Danks (PRD) syndrome confirming pre- and postnatal growth failure, microcephaly, severe mental retardation, seizures, and a distinctive facial appearance; a deletion of 4p16.3 was seen in all eight patients studied with fluorescence in situ hybridisation (FISH). Eleven subjects had a new syndrome with physical overgrowth, heavy facial features, and mild to moderate mental handicap; a duplication of the chromosome region 4p16.3 was found in the four subjects studied. It is suggested that the growth abnormalities in these two families may be explained by a dosage effect of the fibroblast growth factor receptor gene 3 (FGFR3), which is located at 4p16.3, that is, a single dose leads to growth failure and a triple dose to physical overgrowth. We describe the molecular mapping of the translocation breakpoint and define it to within locus D4S43.