Discordance for Skeletal and Cardiac Defect in Monozygotic Twins

Clinical description of 41 Brazilian patients with oculo-auriculo-vertebral dysplasia

OBJECTIVE

To describe the most prominent clinical features of a cohort of patients with oculo-auriculo-vertebral (OAV) dysplasia in Brazil.

METHOD

A review of medical records of patients with diagnosis of OAV from 1990 to 2010 was performed in a medical genetics center.

RESULTS

41 patients were included in the study. Their average age at diagnosis was 2y 10mo (34,4±48,8 months) and the female proportion was 53.7%. Mean maternal age at patient's birth was 28.5y (min: 17, max: 46y) for mothers and 31.4y (min: 21, max: 51y) for fathers. Most patients (97.5%) had auricular involvement, with facial manifestation in 90.2%, spinal in 65.9%, ocular in 53.7%, 36.6% with cardiovascular involvement, 29.3% urogenital, and 17% of the cases with central nervous system (CNS) involvement. The classic OAV triad was present in only 34%. All patients except one had concomitant problems in other organs or systems.

CONCLUSION

Since the diagnosis of OAV dysplasia relies only on a comprehensive medical evaluation, it is imperative that clinicians be aware of the most common presentation of the syndrome. Once suspected, every patient should undergo a complete medical evaluation of multiple systems including complementary exams. Treatment of these patients is based on surgical correction of malformations and rehabilitation.

The neural crest: a versatile organ system

The neural crest is the name given to the strip of cells at the junction between neural and epidermal ectoderm in neurula-stage vertebrate embryos, which is later brought to the dorsal neural tube as the neural folds elevate. The neural crest is a heterogeneous and multipotent progenitor cell population whose cells undergo EMT then extensively and accurately migrate throughout the embryo. Neural crest cells contribute to nearly every organ system in the body, with derivatives of neuronal, glial, neuroendocrine, pigment, and also mesodermal lineages. This breadth of developmental capacity has led to the neural crest being termed the fourth germ layer. The neural crest has occupied a prominent place in developmental biology, due to its exaggerated migratory morphogenesis and its remarkably wide developmental potential. As such, neural crest cells have become an attractive model for developmental biologists for studying these processes. Problems in neural crest development cause a number of human syndromes and birth defects known collectively as neurocristopathies; these include Treacher Collins syndrome, Hirschsprung disease, and 22q11.2 deletion syndromes. Tumors in the neural crest lineage are also of clinical importance, including the aggressive melanoma and neuroblastoma types. These clinical aspects have drawn attention to the selection or creation of neural crest progenitor cells, particularly of human origin, for studying pathologies of the neural crest at the cellular level, and also for possible cell therapeutics. The versatility of the neural crest lends itself to interlinked research, spanning basic developmental biology, birth defect research, oncology, and stem/progenitor cell biology and therapy.

Prevalence, prenatal diagnosis and clinical features of oculo-auriculo-vertebral spectrum: a registry-based study in Europe

Oculo-auriculo-vertebral spectrum is a complex developmental disorder characterised mainly by anomalies of the ear, hemifacial microsomia, epibulbar dermoids and vertebral anomalies. The aetiology is largely unknown, and the epidemiological data are limited and inconsistent. We present the largest population-based epidemiological study to date, using data provided by the large network of congenital anomalies registries in Europe. The study population included infants diagnosed with oculo-auriculo-vertebral spectrum during the 1990-2009 period from 34 registries active in 16 European countries. Of the 355 infants diagnosed with oculo-auriculo-vertebral spectrum, there were 95.8% (340/355) live born, 0.8% (3/355) fetal deaths, 3.4% (12/355) terminations of pregnancy for fetal anomaly and 1.5% (5/340) neonatal deaths. In 18.9%, there was prenatal detection of anomaly/anomalies associated with oculo-auriculo-vertebral spectrum, 69.7% were diagnosed at birth, 3.9% in the first week of life and 6.1% within 1 year of life. Microtia (88.8%), hemifacial microsomia (49.0%) and ear tags (44.4%) were the most frequent anomalies, followed by atresia/stenosis of external auditory canal (25.1%), diverse vertebral (24.3%) and eye (24.3%) anomalies. There was a high rate (69.5%) of associated anomalies of other organs/systems. The most common were congenital heart defects present in 27.8% of patients. The prevalence of oculo-auriculo-vertebral spectrum, defined as microtia/ear anomalies and at least one major characteristic anomaly, was 3.8 per 100,000 births. Twinning, assisted reproductive techniques and maternal pre-pregnancy diabetes were confirmed as risk factors. The high rate of different associated anomalies points to the need of performing an early ultrasound screening in all infants born with this disorder.

Genome-wide scanning reveals complex etiology of oculo-auriculo-vertebral spectrum

Oculo-auriculo-vertebral spectrum (OAVS) is a common developmental disorder involving first and second pharyngeal arches. Although some family cases and such patients showing chromosomal aberrations suggest that OAVS have a genetic basis, no consistent genetic defects have been recorded at present time. Thus, we conducted genetic studies of a three-generation family with five OAVS patients to identify a causative variant for OAVS. Cytogenetic studies revealed those family members had a normal karyotype and no causative mutations were founded in SALL1 and TCOF1, which known to be responsible for two other syndromes that have clinical overlapping with OAVS. Genotyping with commercially available BeadChips was performed on 13 individuals in the same family, showing no significant difference between the affected and normal members in terms of copy number variations (CNVs) in either number or size and no definitive causative CNV. A total of 8,224 informative autosomal SNPs that are evenly distributed throughout the genome were selected for both parametric and non-parametric linkage analysis. Significant negative LOD scores were obtained for the reported OAVS locus, providing further evidence for genetic heterogeneity of this complex disorder. The highest LOD score of 1.60 was noted on chromosome 15q26.2-q26.3 showing a potential linkage to this locus. The variable phenotypes of the affected members and the failure to identify a causative variant indicate that a complex etiology may be present even in a consanguineous family, which makes it more challenging to ascertain the cause of OAVS in further analysis.

Identical but not the same: the value of discordant monozygotic twins in genetic research

Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called "genetically identical"; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post-zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders.

Syndromes of the first and second pharyngeal arches: A review

Our aim in this review is to discuss currently known mechanisms associated with three important syndromes of the first and second pharyngeal arches: Treacher Collins syndrome (TCS), Oculo-auriculo-vertebral syndrome (AOVS) and Auriculo-Condylar syndrome (ACS) or question mark ear syndrome. TCS and ACS are autosomal dominant diseases, with nearly complete penetrance and wide spectrum of clinical variability. The phenotype of the latter has several overlapping features with OAVS, but OAVS may exist in both sporadic and autosomal dominant forms. Mutations in the TCOF1 gene are predicted to cause premature termination codons, leading to haploinsuficiency of the protein treacle and causing TCS. Low amount of treacle leads ultimately to a reduction in the number of cranial neural crest cells migrating to the first and second pharyngeal arches. Other than TCS, the genes associated with ACS and OAVS are still unknown. The first locus for ACS was mapped by our group to 1p21-23 but there is genetic heretogeneity. Genetic heterogeneity is also present in OAVS. Based on the molecular analysis of balanced translocation in an OAVS patient, it has been suggested that abnormal expression of BAPX1 possibly due to epigenetic disregulation might be involved with the etiology of OAVS. Involvement of environmental events has also been linked to the causation of OAVS. Identification of factors leading to these disorders are important for a comprehensive delineation of the molecular pathways underlying the craniofacial development from the first and the second pharyngeal arches, for genetic counseling and to open alternative strategies for patient treatment.

Goldenhar syndrome in association with agenesia of the internal carotid artery

The association between Goldenhar syndrome and homolateral internal carotid artery agenesis to our knowledge, has never emerged before. We present a case report in a female child that was examined with tonal audiometry, A.B.R., CT scan, MR, digital-subtraction-angiography and color Doppler. The aim of this report is to present an uncommon pathologic association which also provides a brief review of the embryology of the ear and carotid vessels whilst discussing probable pathogenetic causes.

Reproduction abnormalities and twin pregnancies in parents of sporadic patients with oculo-auriculo-vertebral spectrum/Goldenhar syndrome

A great number of case reports on concordant and discordant twins with oculo-auriculo-vertebral spectrum (OAVS) suggest that there might be an association between reproductive abnormalities, twinning and OAVS. The etiology of OAVS is unknown, but may involve epigenetic dysregulation of the oocyte or early embryo. We collected data on fertility and pregnancy outcome of 72 parents of patients with sporadic OAVS. We also evaluated prospective follow-up data on 3.372 fetuses and children conceived by intracytoplasmatic sperm injection (ICSI). Parental age, duration of menstrual cycle and the incidence of spontaneous abortion was not different when compared to the German population. However, there is an excess of parents who have used assisted reproductive techniques (ART; retrospective P = 0.038, prospective P = 0.023) and an excess of twins among naturally conceived patients with OAVS (P = 0.0025). An excess of ART conceptions and monozygotic twinning in OAVS is compatible with the concept of overripeness ovopathy as proposed by Jongbloet (Maandschr Kindergeneeskd 36:352-367, 1968).

Hemifacial microsomia and treatment options for auricular replacement: A review of the literature

STATEMENT OF PROBLEM

Although surgical reconstruction is the treatment of choice for auricular deformities that result from hemifacial microsomia, the implant-retained auricular prosthesis must be considered when surgical reconstruction is not possible. The competent and successful practitioner should be knowledgeable of the nature of this congenital disease.

PURPOSE

This article reviewed the first and second branchial syndrome, treatment approaches, and potential advances in surgical and prosthetic rehabilitation for patients with hemifacial microsomia.

CONCLUSION

Advantages and disadvantages of autogenous and alloplastic ear reconstructions are discussed. New research initiatives, such as tissue engineering and fabrication of auricular prosthesis by CAD/CAM, offer the potential for improved treatment for the future treatment of hemifacial microsomia.

Discordance of signs in monozygotic twins concordant for the Goldenhar anomaly

Concordance for Goldenhar anomaly has been described in monozygotic (MZ) twins on 2 occasions but never in dizygotic (DZ) twins. In both cases the twins were similarly, although not identically, affected. We report on a pair of probably monozygotic twins (8% probability of DZ) who presented with extremely diverse manifestations of this anomaly complex. One of them required a tracheostomy because of obstructive apnea due to severe micrognathia and subsequently died. This twin had a midline lower lip cleft which has not previously been described in the Goldenhar anomaly.

Goldenhar syndrome and overlapping dysplasias, in vitro fertilisation and ovopathy

In contrast to the opinion of Yovich et al, who documented Goldenhar syndrome in one of possibly monozygous twin brothers conceived by in vitro fertilisation and embryo transfer, I suggest that ovopathy is the cause of this anomaly. The eight criteria which have to be met before a condition can be said to be caused by overripeness ovopathy are shown to be satisfied. My conclusion remains that, in general, sporadically occurring Goldenhar variants, as distinct from familial cases, should be considered to be just casualities in the broad 'continuum of reproductive wastage' seen in high risk conceptions, one of which is IVF. This concept increases our understanding of human variation not satisfactorily explained by Mendelian inheritance.