Clinical Presentations and Diagnostic Imaging of VACTERL Association.

Background: VACTERL association consists of Vertebral, Anorectal, Cardiac, Tracheo-Esophageal, Renal, and Limb defects. The diagnosis depends on the presence of at least three of these structural abnormalities. Methods: The clinical presentation and diagnostic prenatal imaging of VACTERL association are comprehensively reviewed. Results: The most common feature is a vertebral anomaly, found in 60-80% of cases. Tracheo-esophageal fistula is seen in 50-80% of cases and renal malformations in 30% of patients. Limb defects including thumb aplasia/hypoplasia, polydactyly, and radial agenesis/hypoplasia are present in 40-50% of cases. Anorectal defects, like imperforate anus/anal atresia, are challenging to detect prenatally. Conclusion: The diagnosis of VACTERL association mostly relies on imaging techniques such as ultrasound, computed tomography, and magnetic resonance. Differential diagnosis should exclude similar diseases such as CHARGE and Townes-Brocks syndromes and Fanconi anemia. New insights into genetic etiology have led to recommendations of chromosomal breakage investigation for optimal diagnosis and counseling.

Tbx5 inhibits hedgehog signaling in determination of digit identity.

Dominant TBX5 mutation causes Holt-Oram syndrome (HOS), which is characterized by limb defects in humans, but the underlying mechanistic basis is unclear. We used a mouse model with Tbx5 conditional knockdown in Hh-receiving cells (marked by Gli1+) during E8 to E10.5, a previously established model to study atrial septum defects, which displayed polydactyly or hypodactyly. The results suggested that Tbx5 is required for digit identity in a subset of limb mesenchymal cells. Specifically, Tbx5 deletion in this cell population decreased cell apoptosis and increased the proliferation of handplate mesenchymal cells. Furthermore, Tbx5 was found to negatively regulate the Hh-signaling activity through transcriptional regulation of Ptch1, a known Hh-signaling repressor. Repression of Hh-signaling through Smo co-mutation in Tbx5 heterozygotes rescued the limb defects, thus placing Tbx5 upstream of Hh-signaling in limb defects. This work reveals an important missing component necessary for understanding not only limb development but also the molecular and genetic mechanisms underlying HOS.

Identification of a novel TBX5 c.755 + 1 G > A variant and related pathogenesis in a family with Holt-Oram syndrome.

The proband with congenital heart disease and abnormal thumb was clinically diagnosed as Holt-Oram syndrome (HOS). A novel variant, T-box transcription factor 5 (TBX5) c.755 + 1 G > A, was identified in the proband via whole exome sequencing and validated using Sanger sequencing. Pedigree analysis and clinical examinations revealed three/seven individuals over three generations within the family, with features suggestive of HOS. Deep amplicon sequencing confirmed that the allele frequencies of the novel variant in the proband (III-1), her brother (III-2), and her mother (II-2) were 50%, 48.3%, and 38.1%, respectively, indicating that III-1 and III-2 harbored heterozygous variants, while II-2 harbored mosaic heterozygous variants. The minigene splicing assay showed that the novel variant affected the normal splicing of exon 7, resulting in the production of abnormal TBX5 transcripts. Reverse transcription-quantitative polymerase chain reaction and western blot analyses revealed that the novel variant upregulated TBX5 expression at the transcriptional and translational levels. Nuclear localization assay demonstrated impaired nuclear localization of the mutant TBX5. Cell viability assay revealed the inhibition of cell activity by the mutant TBX5. Our findings indicate that the novel variant was potentially induced HOS, probably by causing aberrant splicing, reducing the enrichment of nuclear TBX5 protein, and inhibiting cellular proliferation.

Thrombocytopenia-Absent Radius Syndrome: Descriptions of Three New Cases and a Novel Splicing Variant in RBM8A That Expands the Spectrum of Null Alleles.

Thrombocytopenia-absent radius (TAR) syndrome is a rare congenital disorder characterized by the bilateral absence of the radius and thrombocytopenia, and sometimes by other skeletal, gastrointestinal, cardiac, and renal abnormalities. The underlying genetic defect is usually the compound inheritance of a microdeletion in 1q21.1 (null allele) and a low-frequency, non-coding single nucleotide variant (SNV) in the RBM8A gene (hypomorphic allele). We report three new cases from two unrelated families. The two siblings presented the common genotype, namely the compound heterozygosity for a 1q21.1 microdeletion and the hypomorphic SNV c.-21G>A in RBM8A, whereas the third, unrelated patient presented a rare genotype comprised by two RBM8A variants: c.-21G>A (hypomorphic allele) and a novel pathogenic variant, c.343-2A>G (null allele). Of the eight documented RBM8A variants identified in TAR syndrome patients, four have hypomorphic expression and four behave as null alleles. The present report expands the RBM8A null allele spectrum and corroborates the particularities of RBM8A involvement in TAR syndrome pathogenesis.

Functional analysis of two novel TBX5 variants present in individuals with Holt-Oram syndrome with different clinical manifestations.

Holt-Oram syndrome (HOS) is a rare disorder characterized by cardiac and upper-limb defects. Pathogenic variants in TBX5-a gene encoding a transcription factor important for heart and skeletal development-are the only known cause of HOS. Here, we present the identification and functional analysis of two novel TBX5 pathogenic variants found in two individuals with HOS presenting distinct phenotypes. The individual with the c.905delA variant has a severe cardiac phenotype but mild skeletal defects, unlike the individual with the c.246_249delGATG variant who has no cardiac problems but severe upper limbs malformations, including phocomelia. Both frameshift variants, c.246_249delGATG and c.905delA, generate mRNAs harbouring premature stop codons which, if not degraded by nonsense mediated decay, will lead to the production of shorter TBX5 proteins, p.Gln302Argfs*92 and p.Met83Phefs*6, respectively. Immunocytochemistry results suggest that both mutated proteins are produced and furthermore, like the wild-type protein, p.Gln302Argfs*92 mutant appears to be mainly localized in the nucleus, in contrast with p.Met83Phefs*6 mutant that displays a higher level of cytoplasmic localization. In addition, luciferase activity analysis revealed that none of the TBX5 mutants are capable of transactivating the NPPA promoter. In conclusion, our results provide evidence that both pathogenic variants cause a severe TBX5 loss-of-function, dramatically reducing its biological activity. The absence of cardiac problems in the individual with the p.Met83Phefs*6 variant supports the existence of other mechanisms/genes underlying the pathogenesis of HOS and/or the existence of an age-related delay in the development of a more serious cardiac phenotype. Further studies are required to understand the differential effects observed in the phenotypes of both individuals.

Expanding the phenotype in Adams-Oliver syndrome correlating with the genotype.

RATIONALE: Adams-Oliver syndrome (AOS) is a genetic disorder characterized by the association of aplasia cutis congenita (ACC), terminal transverse limb defect (TTLD), congenital cardiac malformation (CCM), and minor features, such as cutaneous, neurological, and hepatic abnormalities (HAs). The aim of the study is to emphasize phenotype-genotype correlations in AOS. METHODS: We studied 29 AOS patients. We recorded retrospectively detailed phenotype data, including clinical examination, biological analyses, and imaging. The molecular analysis was performed through whole exome sequencing (WES). RESULTS: Twenty-nine patients (100%) presented with ACC, the principal inclusion criteria in the study. Seventeen of twenty-one (81%) had cutis marmorata telangiectasia congenita, 16/26 (62%) had TTLD, 14/23 (61%) had CCM, 7/20 (35%) had HAs, and 9/27 (33%) had neurological findings. WES was performed in 25 patients. Fourteen of twenty-five (56%) had alterations in the genes already described in AOS. CCM and HAs are particularly associated with the NOTCH1 genotype. TTLD is present in patients with DOCK6 and EOGT alterations. Neurological findings of variable degree were associated sometimes with DOCK6 and NOTCH1 rarely with EOGT. CONCLUSION: AOS is characterized by a clinical and molecular variability. It appears that degrees of genotype-phenotype correlations exist for patients with identified pathogenic mutations, underlining the need to undertake a systematic but adjusted multidisciplinary assessment.

Familial dilated cardiomyopathy associated with pathogenic TBX5 variants: Expanding the cardiac phenotype associated with Holt-Oram syndrome.

Holt-Oram syndrome (HOS) is a rare, autosomal dominant disorder caused by heterozygous pathogenic variants in cardiac T-box transcription factor, TBX5. Classically, it is associated with upper limb malformations and variable cardiac abnormalities. Limb manifestations are considered to be invariably present, ranging in severity from limitation in movement, to triphalangeal thumbs, absent thumbs, shortened forearms, or phocomelia. Cardiac involvement is characterized by congenital heart defects, most commonly septal structural malformations, and conduction system disease. Recently, novel TBX5 variants have also been reported in association with dilated cardiomyopathy (DCM). In this context, we report eight individuals from four unrelated families, in whom pathogenic variants in TBX5 segregated with an atypical HOS phenotype. Affected individuals exhibit relatively mild skeletal features of HOS, with a predominant cardiac phenotype, which includes several individuals affected by non-ischaemic DCM. To our knowledge, these represent the first reported cases of DCM in families with skeletal features of HOS, some of whom also harbored variants previously linked to a classical HOS phenotype (p. Arg279* and p.Arg237Gln). This finding supports diverse roles of TBX5 in cardiovascular development and function, and confirms the importance of long-term cardiac surveillance for individuals affected by HOS. Furthermore, these families highlight the wide phenotypic variability of HOS, which may include comparatively mild upper limb findings in respect to cardiac manifestations.

KLF13 is a genetic modifier of the Holt-Oram syndrome gene TBX5.

TBX5, a member of the T-box family of transcription factors, is a dosage sensitive regulator of heart development. Mutations in TBX5 are responsible for Holt-Oram Syndrome, an autosomal dominant disease with variable and partially penetrant cardiac defects suggestive of the existence of genetic and environmental modifiers. KLF13, a member of the Krüppel-like family of zinc finger proteins is co-expressed with TBX5 in several cardiac cells including atrial cardiomyocytes and cells of the interatrial septum. We report that KLF13 interacts physically and functionally with TBX5 to synergistically activate transcription of cardiac genes. We show that TBX5 contacts KLF13 via its T-domain and find that several disease-causing mutations therein have decreased KLF13 interaction. Whereas Klf13 heterozygote mice have no detectable cardiac defects, loss of a Klf13 allele in Tbx5 heterozygote mice significantly increases the penetrance of TBX5-dependent cardiac abnormalities including atrial, atrial-ventricular and ventricular septal defects. The results reveal for the first time combinatorial interaction between a T-box protein and a KLF family member and its importance for heart and possibly other organ development. The data also suggest that, in human, KLF13 may be a genetic modifier of the Holt-Oram Syndrome gene TBX5.

Langerhans cell histiocytosis and multiple reticulohistiocytomas in a patient with TAR syndrome: An association not previously described.

We describe a patient with thrombocytopenia-absent radius (TAR) syndrome, multisystemic Langerhans cell histiocytosis and multiple reticulohistiocytomas. A mutational study by massive sequencing identified the Val600Glu (V600E) BRAF mutation in the Langerhans cell histiocytosis lesions, but no molecular alterations were found in the reticulohistiocytoma lesions. The concomitant presence in the same patient of more than one type of histiocytosis from two different groups recognized in the most recent Histiocyte Society classification is an extremely rare event. Our case is the first reported case of multisystemic Langerhans cell histiocytosis and multiple reticulohistiocytomas in a patient with TAR syndrome.

Tbx5 Buffers Inherent Left/Right Asymmetry Ensuring Symmetric Forelimb Formation.

The forelimbs and hindlimbs of vertebrates are bilaterally symmetric. The mechanisms that ensure symmetric limb formation are unknown but they can be disrupted in disease. In Holt-Oram Syndrome (HOS), caused by mutations in TBX5, affected individuals have left-biased upper/forelimb defects. We demonstrate a role for the transcription factor Tbx5 in ensuring the symmetric formation of the left and right forelimb. In our mouse model, bilateral hypomorphic levels of Tbx5 produces asymmetric forelimb defects that are consistently more severe in the left limb than the right, phenocopying the left-biased limb defects seen in HOS patients. In Tbx hypomorphic mutants maintained on an INV mutant background, with situs inversus, the laterality of defects is reversed. Our data demonstrate an early, inherent asymmetry in the left and right limb-forming regions and that threshold levels of Tbx5 are required to overcome this asymmetry to ensure symmetric forelimb formation.

Impact of genetic variants on haematopoiesis in patients with thrombocytopenia absent radii (TAR) syndrome.

Thrombocytopenia absent radii (TAR) syndrome is clearly defined by the combination of radial aplasia and reduced platelet counts. The genetics of TAR syndrome has recently been resolved and comprises a microdeletion on Chromosome 1 including the RBM8A gene and a single nucleotide polymorphism (SNP) either at the 5' untranslated region (5'UTR) or within the first intron of RBM8A. Although phenotypically readily diagnosed after birth, the genetic determination of particular SNPs in TAR syndrome harbours valuable information to evaluate disease severity and treatment decisions. Here, we present clinical data in a cohort of 38 patients and observed that platelet counts in individuals with 5'UTR SNP are significantly lower compared to patients bearing the SNP in intron 1. Moreover, elevated haemoglobin values could only be assessed in patients with 5'UTR SNP whereas white blood cell count is unaffected, indicating that frequently observed anaemia in TAR patients could also be SNP-dependent whereas leucocytosis does not correlate with genetic background. However, this report on a large cohort provides an overview of important haematological characteristics in TAR patients, facilitating evaluation of the various traits in this disease and indicating the importance of genetic validation for TAR syndrome.

Congenital heart diseases and their association with the variant distribution features on susceptibility genes.

Congenital heart disease (CHD), one of the causes of childhood morbidity and mortality, is mainly triggered by a combination of environmental and genetic factors. Several susceptible genes, such as NKX2-5, GATA4 and TBX5, have been reported as closely related to heart and vessel development. CHD subtypes are classified into diverse clinical phenotypes, such as atrial septal defects (ASD), ventricular septal defects (VSD), tetralogy of Fallot (TOF), and Holt-Oram syndrome (HOS). Here, we summarize the associations of the genetic variants in these three genes with CHD subtypes. CHD-associated variants of NKX2-5 locate mainly in the tinman domain and the homeodomain. Mutations in the homeodomain are correlated with ASD and atrioventricular (AV) block subtypes. VSD-associated variants of GATA4 are mainly at its terminal ends. Variants of TBX5 gene are primarily in exons 3, 4, 5 and 7 and highly associated with HOS subtype. Hence, the variant distribution of NKX2-5, GATA4 and TBX5 are tightly associated with particular CHD subtypes. Further structure-modelling analysis revealed that these mutated amino acid residuals maintain their DNA-binding ability and structural stability. Therefore structural features of these genes may be used to predict the high risk of CHD subtypes in infants.

Upper Limb Dimelia.

A patient with upper limb dimelia including a double scapula, humerus, radius, and ulna, 11 metacarpals and digits (5 on the superior side, 6 on the inferior side) was treated with a simple amputation of the inferior limb resulting in cosmetic improvement and maintenance of range of motion in the preserved limb. During the amputation, the 2 limbs were found to be anatomically separate except for the ulnar nerve, which, in the superior limb, bifurcated into the sensory branch of radial nerve in the inferior limb, and the brachial artery, which bifurcated into the radial artery. Each case of this rare anomaly requires its own individually carefully planned surgical procedure.

Exome sequencing identifies a c.148-1G>C mutation of TBX5 in a Holt-Oram family with unusual genotype-phenotype correlations.

BACKGROUND/AIMS: Congenital heart defects (CHD) can occur with upper limbs deformities. Holt-Oram syndrome is the main type of heart-hand syndromes, characterized by upper limb radial ray malformations, CHD and/or conduction abnormalities. Mutations of the TBX5 gene, most of which are found within the T-box domain, are one cause of the disease. We aimed to find the cause of the disease in a family with two children exhibiting symptoms of Holt-Oram syndrome while the parents tend to be normal. METHODS: Chromosomal microarray analysis and exome sequencing were applied in the proband segments bearing the specific mutation and single nucleotide variants (SNVs) suspected of being involved in the disease were analyzed by polymerase chain reaction and direct sequencing. RESULTS: A splice acceptor site mutation c.148-1G>C of TBX5 was detected in both the father and the proband. The mutation may result in an aberrant transcript which will most probably undergo nonsense-mediated decay (NMD) system resulting in haploinsufficiency of TBX5 protein. In the meantime, 3 candidated SNVs were detected. CONCLUSIONS: c.148-1G>C of TBX5 should be the pathogenic cause of the disease in this family. Works have been done to find a possible explanation of the unusual genotype-phenotype correlations in this family and further studies are still needed.

A unique TBX5 microdeletion with microinsertion detected in patient with Holt-Oram syndrome.

Holt-Oram syndrome (HOS) is an autosomal dominant condition characterized by upper limb and congenital heart defects and caused by numerous germline mutations of TBX5 producing preterminal stop codons. Here, we report on a novel and unusual heterozygous TBX5 microdeletion with microinsertion (microindel) mutation (c.627delinsGTGACTCAGGAAACGCTTTCCTGA), which is predicted to synthesize a truncated TBX5 protein, detected in a sporadic patient with clinical features of HOS prenatally diagnosed by ultrasonography. This uncommon and relatively large inserted sequence contains sequences derived from nearby but not adjacent templates on both sense and antisense strands, suggesting two possible models, which require no repeat sequences, causing this complex microindel through the bypass of large DNA adducts via an error-prone DNA polymerase-mediated translesion synthesis.

Cervical spine malformation in cornelia de lange syndrome: a report of three patients.

Cornelia de Lange syndrome (CdLS) is a complex genetic disease with skeletal involvement mostly related to upper limb malformations. We report on three males with clinical and molecular diagnoses of CdLS. Besides typical CdLS features, all showed different cervical spine malformations. To the best of our knowledge, this is an unusual malformation in the CdLS phenotypic spectrum.

Whorled hairless nevus of the scalp, linear hyperpigmentation, and telangiectatic nevi of the lower limbs: a novel variant of the "phacomatosis complex".

The term "phacomatosis" refers to a growing number of sporadic genetic skin disorders characterized by the combination of two or more different nevi and possibly resulting from non-allelic twin spotting. While phacomatosis pigmentovascularis (PPV) and pigmentokeratotica represent the most common patterns, some patients do not fit with either condition and are temporarily classified as unique phenotypes. We report on an 8-year-old boy with striking right hemihypoplasia, resulting in limb asymmetry and fixed dislocation of right hip. Skin on the affected side showed three distinct nevi: (i) A whorled, hairless nevus of the scalp in close proximity with (ii) epidermal hyperpigmentation following lines of Blaschko on the neck and right upper limb, and (iii) multiple telangiectatic nevi of the right lower limb and hemiscrotum. Didymosis atricho-melanotica was proposed for the combination of adjacent patchy congenital alopecia and linear hyperpigmentation, while phacomatosis atricho-pigmento-vascularis appears to define the entire cutaneous phenotype, thus implying the involvement of three neighboring loci influencing the development of distinct constituents of the skin. Given the striking asymmetry of the observed phenotype, the effect of mosaicism (either genomic or functional) for a mutation in a single gene with pleiotropic action and influenced by the lateralization pattern of early development cannot be excluded.

Hand and upper limb anomalies in Poland syndrome: a new proposal of classification.

BACKGROUND: The Poland anomaly (PA) comprises unilateral absence or hypoplasia of the pectoralis major muscle and a variable degree of ipsilateral hand and upper limb anomalies. Various hand and upper limb anomalies classifications in PA have been previously published. In this work, a new classification of hand and upper limb anomalies in PA is proposed, on the basis of the clinical and instrumental evaluation of 175 patients. METHODS: The patients have been followed by a multidisciplinary approach, consisting in orthopaedic, surgical, and genetic evaluation and chest, upper limb, and ultrasound examination of major and minor pectoralis muscles, heart, and kidney. RESULTS: Hand and upper limb anomalies were classified in 8 groups on the basis of the clinical degree of severity and on the basis of the presence of coexisting associated anomalies. Data regarding the sex and laterality, previously reported in the medical literature, were confirmed by our analysis. Etiopathogenetic mechanisms leading to the anomaly are discussed. CONCLUSIONS: The proposed classification is derived from the observation of the widest group of patients described in the medical literature. Our proposal could help in the management of patients affected by Poland syndrome and in understanding etiological and pathologic aspects of the disease. LEVEL OF EVIDENCE: IV.

Textiloma mimicking a pericardial hydatid cyst: a case report.

Textiloma is unusual and uncommon diagnosis which is rarely considered. We report the case of a 13 year-old patient with Holt-Oram syndrome. He was operated on in 2006 for ostium secundum atrial septal defect. The postoperative course was uneventful until 2010 when the child presented paroxysmal dyspnoea. Investigations revealed para-cardiac mass which was thought to be a hydatid cyst, but operative findings showed textiloma.