[show abstract][hide abstract] ABSTRACT: Brittle cornea syndrome (BCS) is an autosomal recessive disorder characterised by extreme corneal thinning and fragility. Corneal rupture can therefore occur either spontaneously or following minimal trauma in affected patients. Two genes, ZNF469 and PRDM5, have now been identified, in which causative pathogenic mutations collectively account for the condition in nearly all patients with BCS ascertained to date. Therefore, effective molecular diagnosis is now available for affected patients, and those at risk of being heterozygous carriers for BCS. We have previously identified mutations in ZNF469 in 14 families (in addition to 6 reported by others in the literature), and in PRDM5 in 8 families (with 1 further family now published by others). Clinical features include extreme corneal thinning with rupture, high myopia, blue sclerae, deafness of mixed aetiology with hypercompliant tympanic membranes, and variable skeletal manifestations. Corneal rupture may be the presenting feature of BCS, and it is possible that this may be incorrectly attributed to non-accidental injury. Mainstays of management include the prevention of ocular rupture by provision of protective polycarbonate spectacles, careful monitoring of visual and auditory function, and assessment for skeletal complications such as developmental dysplasia of the hip. Effective management depends upon appropriate identification of affected individuals, which may be challenging given the phenotypic overlap of BCS with other connective tissue disorders.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Jeune asphyxiating thoracic dystrophy (JATD) is a rare, often lethal, recessively inherited chondrodysplasia characterised by shortened ribs and long bones, sometimes accompanied by polydactyly, and renal, liver and retinal disease. Mutations in intraflagellar transport (IFT) genes cause JATD, including the IFT dynein-2 motor subunit gene DYNC2H1. Genetic heterogeneity and the large DYNC2H1 gene size have hindered JATD genetic diagnosis. AIMS AND METHODS: To determine the contribution to JATD we screened DYNC2H1 in 71 JATD patients JATD patients combining SNP mapping, Sanger sequencing and exome sequencing. RESULTS AND CONCLUSIONS: We detected 34 DYNC2H1 mutations in 29/71 (41%) patients from 19/57 families (33%), showing it as a major cause of JATD especially in Northern European patients. This included 13 early protein termination mutations (nonsense/frameshift, deletion, splice site) but no patients carried these in combination, suggesting the human phenotype is at least partly hypomorphic. In addition, 21 missense mutations were distributed across DYNC2H1 and these showed some clustering to functional domains, especially the ATP motor domain. DYNC2H1 patients largely lacked significant extra-skeletal involvement, demonstrating an important genotype-phenotype correlation in JATD. Significant variability exists in the course and severity of the thoracic phenotype, both between affected siblings with identical DYNC2H1 alleles and among individuals with different alleles, which suggests the DYNC2H1 phenotype might be subject to modifier alleles, non-genetic or epigenetic factors. Assessment of fibroblasts from patients showed accumulation of anterograde IFT proteins in the ciliary tips, confirming defects similar to patients with other retrograde IFT machinery mutations, which may be of undervalued potential for diagnostic purposes.
Journal of Medical Genetics 03/2013; · 5.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: From data collected via a large international collaborative study, we have constructed a growth chart for patients with molecularly confirmed congenital spondylo-epiphyseal dysplasia (SEDC) and other COL2A1 related dysplasias. The growth chart is based on longitudinal height measurements of 79 patients with glycine substitutions in the triple-helical domain of COL2A1. In addition, measurements of 27 patients with other molecular defects, such as arginine to cysteine substitutions, splice mutations, and mutations in the C-terminal propeptide have been plotted on the chart. Height of the patients progressively deviate from that of normal children: compared to normal WHO charts, the mean length/height is -2.6 SD at birth, -4.2 SD at 5 years, and -5.8 SD in adulthood. The mean adult height (male and female combined) of patients with glycine substitutions in the triple-helical region is 138.2 cm but there is a large variation. Patients with glycine to cysteine substitutions tend to cluster within the upper part of the chart, while patients with glycine to serine or valine substitutions are situated between +1 SD and -1 SD. Patients with carboxy-terminal glycine substitutions tend to be shorter than patients with amino-terminal substitutions, while patients with splice mutations are relatively tall. However, there are exceptions and specific mutations can have a strong or a relatively mild negative effect on growth. The observation of significant difference in adult height between affected members of the same family indicates that height remains a multifactorial trait even in the presence of a mutation with a strong dominant effect.
American Journal of Medical Genetics Part C Seminars in Medical Genetics 07/2012; 160C(3):205-16. · 4.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Excessive growth of terminal hair around the elbows (hypertrichosis cubiti) has been reported both in isolation and in association with a variable spectrum of associated phenotypic features. We identified a cohort of six individuals with hypertrichosis cubiti associated with short stature, intellectual disability, and a distinctive facial appearance, consistent with a diagnosis of Wiedemann-Steiner syndrome (WSS). Utilizing a whole-exome sequencing approach, we identified de novo mutations in MLL in five of the six individuals. MLL encodes a histone methyltransferase that regulates chromatin-mediated transcription through the catalysis of methylation of histone H3K4. Each of the five mutations is predicted to result in premature termination of the protein product. Furthermore, we demonstrate that transcripts arising from the mutant alleles are subject to nonsense-mediated decay. These findings define the genetic basis of WSS, provide additional evidence for the role of haploinsufficency of histone-modification enzymes in multiple-congenital-anomaly syndromes, and further illustrate the importance of the regulation of histone modification in development.
The American Journal of Human Genetics 07/2012; 91(2):358-64. · 11.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Biallelic mutations in the gene encoding DHOdehase [dihydroorotate dehydrogenase (DHODH)], an enzyme required for de novo pyrimidine biosynthesis, have been identified as the cause of Miller (Genée-Weidemann or postaxial acrofacial dysostosis) syndrome (MIM 263750). We report compound heterozygous DHODH mutations in four additional families with typical Miller syndrome. Complementation in auxotrophic yeast demonstrated reduced pyrimidine synthesis and in vitro enzymatic analysis confirmed reduced DHOdehase activity in 11 disease-associated missense mutations, with 7 alleles showing discrepant activity between the assays. These discrepancies are partly explained by the domain structure of DHODH and suggest both assays are useful for interpretation of individual alleles. However, in all affected individuals, the genotype predicts that there should be significant residual DHOdehase activity. Urine samples obtained from two mutation-positive cases showed elevated levels of orotic acid (OA) but not dihydroorotate (DHO), an unexpected finding since these represent the product and the substrate of DHODH enzymatic activity, respectively. Screening of four unrelated cases with overlapping but atypical clinical features showed no mutations in either DHODH or the other de novo pyrimidine biosynthesis genes (CAD, UMPS), with these cases also showing normal levels of urinary OA and DHO. In situ analysis of mouse embryos showed Dhodh, Cad and Umps to be strongly expressed in the pharyngeal arch and limb bud, supporting a site- and stage-specific requirement for de novo pyrimidine synthesis. The developmental sensitivity to reduced pyrimidine synthesis capacity may reflect the requirement for an exceptional mitogenic response to growth factor signalling in the affected tissues.
Human Molecular Genetics 06/2012; 21(18):3969-83. · 7.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cantú syndrome is characterized by congenital hypertrichosis, distinctive facial features, osteochondrodysplasia and cardiac defects. By using family-based exome sequencing, we identified a de novo mutation in ABCC9. Subsequently, we discovered novel dominant missense mutations in ABCC9 in 14 of the 16 individuals with Cantú syndrome examined. The ABCC9 protein is part of an ATP-dependent potassium (K(ATP)) channel that couples the metabolic state of a cell with its electrical activity. All mutations altered amino acids in or close to the transmembrane domains of ABCC9. Using electrophysiological measurements, we show that mutations in ABCC9 reduce the ATP-mediated potassium channel inhibition, resulting in channel opening. Moreover, similarities between the phenotype of individuals with Cantú syndrome and side effects from the K(ATP) channel agonist minoxidil indicate that the mutations in ABCC9 result in channel opening. Given the availability of ABCC9 antagonists, our findings may have direct implications for the treatment of individuals with Cantú syndrome.
[show abstract][hide abstract] ABSTRACT: The differential diagnosis of a neonate or fetus presenting with a bell-shaped or long narrow thorax includes a wide range of bony dysplasia syndromes. Where this is accompanied by respiratory distress, asphyxiating thoracic dystrophy (ATD, Jeune syndrome) is an important potential diagnosis. Shwachman-Diamond syndrome (SDS) is widely recognised as a cause of exocrine pancreatic dysfunction, short stature and bone marrow failure. It is not so well appreciated that rib and/or thoracic cage abnormalities occur in 30-50% of patients and that, in severe cases, these abnormalities may lead to thoracic dystrophy and respiratory failure in the newborn. There are, however, at least three previous case reports of children who were initially diagnosed with ATD who were subsequently shown to have SDS.
This report details the case history of a patient misdiagnosed as having ATD as a neonate following the neonatal asphyxial death of her brother. She subsequently developed progressive pancytopenia but was only diagnosed with SDS at 11 years of age after referral for haematopoietic stem cell transplantation for bone marrow failure accompanied by trilineage dysplasia and clonal cytogenetic abnormalities on bone marrow examination. Subsequent testing revealed the presence of fat globules in stools, reduced faecal chymotrypsin, fat-soluble vitamin deficiency, metaphyseal dysplasia on skeletal survey and heterozygous mutations of the SBDS gene.
This report highlights the potential for diagnostic confusion between ATD and SDS. It is important to include SDS in the differential diagnosis of newborns with thoracic dystrophy and to seek expert clinical and radiological assessment of such children.
[show abstract][hide abstract] ABSTRACT: The mucopolysaccaridoses are a collection of rare genetic conditions where there is a defect in lysosomal storage causing an accumulation of glycosaminoglycans. There are seven different forms of mucopolysaccaridosis (MPS), each with a different enzymatic mutation and thus each form has similar but separate clinical features. There are multiple effects of glycosaminoglycan deposition including musculoskeletal manifestations such as joint problems and growth arrests. Common treatments of the orthopaedic complications include hip arthroplasty, cervical spine surgery and epiphyseal stapling to correct genu valgum. Presently, the only curative treatment for MPS is haematopoietic stem cell transplantation. Enzyme replacement therapy is a future target for all forms of MPS and a range of therapies are currently in development.
[show abstract][hide abstract] ABSTRACT: Sex chromosome trisomies (SCTs) are found on amniocentesis in 2.3-3.7 per 1000 same-sex births, yet there is a limited database on which to base a prognosis. Autism has been described in postnatally diagnosed cases of Klinefelter syndrome (XXY karyotype), but the prevalence in non-referred samples, and in other trisomies, is unclear. The authors recruited the largest sample including all three SCTs to be reported to date, including children identified on prenatal screening, to clarify this issue.
Parents of children with a SCT were recruited either via prenatal screening or via a parental support group, to give a sample of 58 XXX, 19 XXY and 58 XYY cases. Parents were interviewed using the Vineland Adaptive Behavior Scales and completed questionnaires about the communicative development of children with SCTs and their siblings (42 brothers and 26 sisters).
Rates of language and communication problems were high in all three trisomies. Diagnoses of autism spectrum disorder (ASD) were found in 2/19 cases of XXY (11%) and 11/58 XYY (19%). After excluding those with an ASD diagnosis, communicative profiles indicative of mild autistic features were common, although there was wide individual variation.
Autistic features have not previously been remarked upon in studies of non-referred samples with SCTs, yet the rate is substantially above population levels in this sample, even when attention is restricted to early-identified cases. The authors hypothesise that X-linked and Y-linked neuroligins may play a significant role in the aetiology of communication impairments and ASD.
Archives of Disease in Childhood 10/2011; 96(10):954-9. · 3.05 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report an allelic series of eight mutations in GATA2 underlying Emberger syndrome, an autosomal dominant primary lymphedema associated with a predisposition to acute myeloid leukemia. GATA2 is a transcription factor that plays an essential role in gene regulation during vascular development and hematopoietic differentiation. Our findings indicate that haploinsufficiency of GATA2 underlies primary lymphedema and predisposes to acute myeloid leukemia in this syndrome.
[show abstract][hide abstract] ABSTRACT: Bohring-Opitz syndrome is characterized by severe intellectual disability, distinctive facial features and multiple congenital malformations. We sequenced the exomes of three individuals with Bohring-Opitz syndrome and in each identified heterozygous de novo nonsense mutations in ASXL1, which is required for maintenance of both activation and silencing of Hox genes. In total, 7 out of 13 subjects with a Bohring-Opitz phenotype had de novo ASXL1 mutations, suggesting that the syndrome is genetically heterogeneous.
[show abstract][hide abstract] ABSTRACT: Cantú syndrome, a rare disorder of congenital hypertrichosis, characteristic facial anomalies, cardiomegaly, and osteochondrodysplasia was first described in 1982 by Cantú. Twenty-three cases of Cantú syndrome have been reported to date. The pathogenesis of this rare autosomal dominant condition is unknown. We describe 10 patients with Cantú syndrome (9 new cases and the long-term follow-up of a 10th case reported by Robertson in 1999) comparing the phenotype with that of the previously reported cases. We describe how the distinctive facial appearance evolves with time and report several new findings including recurrent infections with low immunoglobulin levels and gastric bleeding in some of our patients. The cardiac manifestations include patent ductus arteriosus, septal hypertrophy, pulmonary hypertension, and pericardial effusions. They may follow a benign course, but of the 10 cases we report, 4 patients required surgical closure of the patent ductus arteriosus and 1 patient a pericardectomy. Long-term follow-up of these patients has shown reassuring neuro-developmental outcome and the emergence of a behavior phenotype including obsessive traits and anxiety.
American Journal of Medical Genetics Part A 02/2011; 155A(3):508-18. · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: Bohring-Opitz syndrome (BOS) is a rare congenital disorder of unknown etiology diagnosed on the basis of distinctive clinical features. We suggest diagnostic criteria for this condition, describe ten previously unreported patients, and update the natural history of four previously reported patients. This is the largest series reported to date, providing a unique opportunity to document the key clinical features and course through childhood. Investigations undertaken to try and elucidate the underlying pathogenesis of BOS using array comparative genomic hybridization and tandem mass spectrometry of cholesterol precursors did not show any pathogenic changes responsible.
European journal of human genetics: EJHG 02/2011; 19(5):513-9. · 3.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: We describe a patient with striking generalized symmetrical enchondromatosis of the tubular bones and a de novo duplication of chromosome 12p11.23 to 12p11.22. The PTHLH gene within this region encodes a ligand for PTHR1: mutations in the gene encoding this receptor are associated with some cases of Ollier disease, several skeletal dysplasias including Blomstrand, Eiken, and Jansen and down-regulation of PTHLH expression in brachydactyly type E. Our findings suggest that abnormal PTHLH-PTHR1 signaling may underly this unusual form of enchondromatosis and indicate that unlike most cases of Ollier disease it is dominantly inherited.
American Journal of Medical Genetics Part A 11/2010; 152A(12):3124-8. · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: Barth Syndrome (BTHS) is an X-linked multisystem disorder (OMIM 302060) usually diagnosed in infancy and characterized by cardiac problems [dilated cardiomyopathy (DCM) ± endocardial fibroelastosis (EFE) ± left ventricular non-compaction (LVNC)], proximal myopathy, feeding problems, growth retardation, neutropenia, organic aciduria and variable respiratory chain abnormalities. We wished to determine whether BTHS had a significant impact on fetal and perinatal health in a large cohort of family groups originating from a defined region.
Case note review on 19 families originating from the UK and known to the Barth Syndrome Service of the Bristol Royal Hospital for Children.
Details are presented on six kindreds (32%) with genetically and biochemically proven BTHS that demonstrate a wider phenotype including male fetal loss, stillbirth and severe neonatal illness or death. In these families, 9 males were stillborn and 14 died as neonates or infants but there were no losses of females. BTHS was definitively proven in five males with fetal onset of DCM ± hydrops/EFE/LVNC.
These findings stress the importance of considering BTHS in the differential diagnosis of unexplained male hydrops, DCM, EFE, LVNC or pregnancy loss, as well as in neonates with hypoglycemia, lactic acidosis and idiopathic mitochondrial disease.
[show abstract][hide abstract] ABSTRACT: Four reports have been published on an association between acute myeloid leukaemia (AML) and primary lymphedema, with or without congenital deafness. We report seven new cases, including one extended family, confirming this entity as a genetic syndrome. The lymphedema typically presents in one or both lower limbs, before the hematological abnormalities, with onset between infancy and puberty and frequently affecting the genitalia. The AML is often preceded by pancytopenia or myelodysplasia with a high incidence of monosomy 7 in the bone marrow (five propositi and two relatives). Associated anomalies included hypotelorism, epicanthic folds, long tapering fingers and/or neck webbing (four patients), recurrent cellulitis in the affected limb (four patients), generalized warts (two patients), and congenital, high frequency sensorineural deafness (one patient). Children with lower limb and genital lymphedema should be screened for hematological abnormalities and immunodeficiency.
American Journal of Medical Genetics Part A 09/2010; 152A(9):2287-96. · 2.30 Impact Factor