Absent Radii Research Articles

Thrombocytopenia and Absent Radii (TAR) Syndrome in Non Identical Twins

This is a case report of female non identical twins with bilateral absent radii and severe thrombocytopenia. Genetic studies confirmed 1q21.1 deletion. A review of literature showed TAR syndrome in 2 pairs of identical twins (reported in 1986) and one pair of non identical twins (reported in 1979). DOI: http://dx.doi.org/10.3126/jnps.v33i2.8378 J Nepal Paediatr Soc. 2013; 33(2):150-151

Prenatal diagnosis and post-mortem examination in a fetus with thrombocytopenia-absent radius (TAR) syndrome due to compound heterozygosity for a 1q21.1 microdeletion and a RBM8A hypomorphic allele: a case report

BackgroundThrombocytopenia–absent radius syndrome is a rare autosomal recessive disorder characterized by megakaryocytic thrombocytopenia and longitudinal limb deficiencies mostly affecting the radial ray. Most patients are compound heterozygotes for a 200 kb interstitial microdeletion in 1q21.1 and a hypomorphic allele in RBM8A, mapping in the deleted segment. At the moment, the complete molecular characterization of thrombocytopenia–absent radius syndrome is limited to a handful of patients mostly ascertained in the pediatric ageCase presentationWe report on a fetus with bilateral upper limb deficiency found at standard prenatal ultrasound examination. The fetus had bilateral radial agenesis and humeral hypo/aplasia with intact thumbs, micrognathia and urinary anomalies, indicating thrombocytopenia–absent radius syndrome. Molecular studies demonstrated compound heterozygosity for the 1q21.1 microdeletion and the RBM8A rs139428292 variant at the hemizygous state, inherited from the mother and father, respectivelyConclusionThe molecular information allowed prenatal diagnosis in the following pregnancy resulting in the birth of a healthy carrier female. A review was carried out with the attempt to the trace the fetal ultrasound presentation of thrombocytopenia–absent radius syndrome and discussing opportunities for second-tier molecular studies within a multidisciplinary setting.

Clinical and mutation data in 12 patients with the clinical diagnosis of Nager syndrome

Nager syndrome (MIM #154400) is the best-known preaxial acrofacial dysostosis, mainly characterized by craniofacial and preaxial limb anomalies. The craniofacial abnormalities mainly consist of downslanting palpebral fissures, malar hypoplasia, micrognathia, external ear anomalies, and cleft palate. The preaxial limb defects are characterized by radial and thumb hypoplasia or aplasia, duplication of thumbs and proximal radioulnar synostosis. Haploinsufficiency of SF3B4 (MIM *605593), which encodes SAP49, a component of the pre-mRNA spliceosomal complex, has recently been identified as the underlying cause of Nager syndrome. In our study, we performed exome sequencing in two and Sanger sequencing of SF3B4 in further ten previously unreported patients with the clinical diagnosis of Nager syndrome, including one familial case. We identified heterozygous SF3B4 mutations in seven out of twelve patients. Four of the seven mutations were shown to be de novo; in three individuals, DNA of both parents was not available. No familial mutations were discovered. Three mutations were nonsense, three were frameshift mutations and one T>C transition destroyed the translation start signal. In three of four SF3B4 negative families, EFTUD2 was analyzed, but no pathogenic variants were identified. Our results indicate that the SF3B4 gene is mutated in about half of the patients with the clinical diagnosis of Nager syndrome and further support genetic heterogeneity for this condition.

Contribution of copy number variants involving nonsense-mediated mRNA decay pathway genes to neuro-developmental disorders

The nonsense-mediated mRNA decay (NMD) pathway functions not only to degrade transcripts containing premature termination codons (PTC), but also to regulate the transcriptome. UPF3B and RBM8A, important components of NMD, have been implicated in various forms of intellectual disability (ID) and Thrombocytopenia with Absent Radius (TAR) syndrome, which is also associated with ID. To gauge the contribution of other NMD factors to ID, we performed a comprehensive search for copy number variants (CNVs) of 18 NMD genes among individuals with ID and/or congenital anomalies. We identified 11 cases with heterozygous deletions of the genomic region encompassing UPF2, which encodes for a direct interacting protein of UPF3B. Using RNA-Seq, we showed that the genome-wide consequence of reduced expression of UPF2 is similar to that seen in patients with UPF3B mutations. Out of the 1009 genes found deregulated in patients with UPF2 deletions by at least 2-fold, majority (95%) were deregulated similarly in patients with UPF3B mutations. This supports the major role of deletion of UPF2 in ID. Furthermore, we found that four other NMD genes, UPF3A, SMG6, EIF4A3 and RNPS1 are frequently deleted and/or duplicated in the patients. We postulate that dosage imbalances of these NMD genes are likely to be the causes or act as predisposing factors for neuro-developmental disorders. Our findings further emphasize the importance of NMD pathway(s) in learning and memory.

Holt- Oram syndrome: a case report

Background : Holt-Oram syndrome (HOS) is mainly an autosomal dominant condition characterized by upperlimb abnormalities and in 85 – 95% of cases, congenital cardiac malformations. It may occur as a result of new mutations in 40% of cases. Methods : We reviewed the case notes of a neonate. Results : We present a case of HOS in a one week old male with an absent radius but no congenital cardiac abnormality born to apparently normal parents. Conclusion : HOS is a rare disease and highlights the need for parental counselling. Key words : Holt-Oram, Congenital Malformations, Phocomelia, Oligodactyly, High Med Res J 2013;13:53-55

Prenatal Diagnosis of Bilateral Ectrodactyly and Radial Agenesis Associated with Trisomy 10 Mosaicism

Ectrodactyly or split hand and foot malformations (SHFMs) are rare malformations of the limbs, characterized by median clefts of the hands and feet, syndactyly, and aplasia and/or hypoplasia of the phalanges. They represent a clinically and genetically heterogeneous disorder, with both sporadic and familial cases. Most of the genomic rearrangements identified to date in some forms of SHFM are autosomal dominant traits, involving various chromosome regions. Bilateral radial ray defects comprise also a large heterogenous group of disorders, including trisomy 18, Fanconi anemia, and thrombocytopenia-absent-radius syndrome, not commonly associated with ectrodactyly. The present paper describes a case of ectrodactyly associated with bilateral radial ray defects, diagnosed in the first trimester of pregnancy, in a fetus affected by trisomy 10. Only four cases of sporadic and isolated ectrodactyly, diagnosed by ultrasonography between 14 and 22 weeks' gestation, have been reported. To our knowledge, the present case is the first report of mosaic trisomy 10 associated with SHFM and radial aplasia. Trisomy 10 is a rare lethal chromosomal abnormality, most frequently found in abortion products. Only six liveborn mosaic trisomy 10 infants, with severe malformations, dead in early infancy, have been reported. A severe clinical syndrome can be defined, comprising ear abnormalities, cleft lip/palate, malformations of eyes, heart, and kidneys, and deformity of hands and feet and most often associated with death neonatally or in early infancy.

P25.13: A case of absent radius in trisomy 18

P25.13: A case of absent radius in trisomy 18

Fetal forearm anomalies: prenatal diagnosis, associations and management strategy

To determine the underlying associations in fetuses with forearm anomalies, and to derive a management strategy to improve prenatal diagnosis and parental counselling. A retrospective review of fetal medicine unit records to identify all cases with an absent, short or abnormal radius and/or ulna. Cases with a generalised skeletal dysplasia were excluded. Fetal medicine, maternal, neonatal and, where appropriate, histopathological reports, were reviewed. Sixty-six cases were identified. Two were lost to follow-up and subsequently omitted. Chromosomal anomalies accounted for 19 cases (29.7%), genetic syndromes for 19 (29.7%) and isolated forearm defects for 15 cases (23%). A definitive postnatal diagnosis was made in 54 cases (84%). In 45 of the 64 (70%) cases, a correct prenatal diagnosis was made. Cases with bilateral lesions had a significantly higher association with aneuploidy and genetic syndromes, while those with a sonographically isolated unilateral forearm defect had a very low incidence of other underlying pathology. Fetuses with bilateral forearm defects or those with unilateral lesions and other abnormalities detected prenatally have a high incidence of aneuploidy and genetic syndromes. Isolated, unilateral lesions usually have a good prognosis. A management strategy is presented to aid accurate prenatal diagnosis and parental counselling.

A novel mutation in the SHH long‐range regulator (ZRS) is associated with preaxial polydactyly, triphalangeal thumb, and severe radial ray deficiency

Sonic Hedgehog (SHH) within the posteriorly located zone of polarizing activity is the main controller of the antero-posterior axis of limb development. The ZRS (zone of polarizing activity regulatory sequence) is a long-range limb-specific SHH enhancer. Several point mutations in the ZRS have been described in humans. These mutations cause enhanced SHH activity and ectopic anterior expression of SHH and a variable phenotype of preaxial polydactyly and triphalangeal thumb. Absent thumb or radius has not been reported with ZRS mutations. Here, we report on a family with a variable phenotype of preaxial polydactyly as well as absent thumb and radius, with kidney and cardiac defects. The family was screened for SALL1, SALL4, and TBX5 mutations, but all were normal. Finally, they were screened for ZRS mutations, which showed a novel point mutation within the ZRS, NG_009240.1: g.106954C>T (traditional nomenclature: ZRS619C>T) in the five affected members. This mutation was not previously reported in any public domain database, and was not found in our healthy and ethnically matched control individuals or unaffected family members. We hypothesize that interactions of SHH and SALL1 explain the overlapping features of the family described here and patients with Townes-Brocks syndrome.

Thrombocytopenia and absent radii (TAR) syndrome associated with bilateral congenital cataract: a case report

IntroductionThrombocytopenia with absent radii is a rare congenital defect with hypomegakaryocytic thrombocytopenia and bilateral radial aplasia that may have additional anomalies. We report the case of a girl baby with thrombocytopenia and absent radii syndrome and bilateral congenital cataract. This anomaly has not been previously reported in the children of a non- consanguineous marriage.Case presentationThis case report describes a two-day-old girl baby of Arab origin with thrombocytopenia and absent radii syndrome and bilateral congenital cataract.ConclusionsThis report describes a finding of bilateral congenital cataract associated with thrombocytopenia and absent radii syndrome that has been reported only once before in the literature. This case report highlights a new ocular manifestation in one of the bone marrow failure syndromes.

A Fetus with Hemifacial Microsomia and Sirenomelia. The Same Mesodermal Defect Spectrum?

Sirenomelia is the most severe malformation complex affecting the human caudal pole, although its etiology is unclear, a primary defect of blastogenesis has been proposed. Studies consider sirenomelia as the most severe form of caudal dysgenesis, VACTERL association, or axial mesodermal dysplasia, although others still support the idea of a different pathologic entity. We report the prenatal, clinical, and pathologic features of a fetus with cleft lip and palate, microtia, cardiac, renal and intestinal malformations, radial aplasia, and sirenomelia. Karyotype, chromosomal breakage studies, and SHH sequence analysis were normal. The occurrence of cephalic, midline-paramedial, and caudal malformations in the same patient imply the diagnosis of hemifacial microsomia and sirenomelia. These entities are part of the same mesodermal malformation spectrum and the clinical presentation depends on environmental and genetic interactions in embrionic development. Future clinical and genome wide studies will help to better delineate this spectrum.

Caudal Dysplasia, Femoral Hypoplasia-Unusual Facies Syndrome and Absent Radius: A New Association in Infant of Diabetic Mother?

The Caudal dysplasia syndrome (CDS) and the femoral hypoplasia-unusual facies syndrome (FHUFS) have been reported to be more frequent among infants of diabetic mothers (IDMs). Infact, uncontrolled maternal diabetes is the most common cause of both the syndromes. Till now, there is no case report to suggest absent radius as a manifestation of IDMs. The authors report a rare case of newborn, who presented with features compatible with both CDS and FHUFS with an additional feature of absent radius, which is not reported in the literature so far. The possibility that all these features represent different manifestations of the same disorder is discussed here.

TAR Syndrome, a Rare Case Report with Cleft Lip/Palate

TAR (Thrombocytopenia-Absent Radius) is a clinicallydefined syndrome characterized by hypomegakarocytic thrombocytopenia and bilateral absence of radius in the presence of both thumbs . We describe a female neonate as a rare case of TAR syndrome with orofacial cleft. Bone marrow aspiration of the patient revealed a cellular marrow with marked reduction of megakaryocytes. Our clinical observation is consistent with TAR syndrome. However, other syndromes with cleft lip/palate and radial aplasia like Roberts syndrome (tetraphocomelia), Edwards syndrome and Fanconi and sc phocomelia (which has less degree of limb reduction) should be considered. Our cytogenetic study excludes other overlapping chromosomal syndromes. RBM8A analysis may reveal nucleotide alteration, leading to definite diagnosis. Our objective is adding this cleft lip and cleft palate to the literature regarding TAR syndrome. - Eva Klopocki, Harald Schulz, Gabriele Straub,Judith Hall,Fabienne Trotier, et al(February 2007) ;Complex inheritance pattern Resembeling Autosomal Recessive Inheritance Involving a Microdeletion in Thrombocytopenia-Absent Radius Syndrome.The American Journal of Human Genetics 80:232-240

De novo CNV analysis implicates specific abnormalities of postsynaptic signalling complexes in the pathogenesis of schizophrenia

A small number of rare, recurrent genomic copy number variants (CNVs) are known to substantially increase susceptibility to schizophrenia. As a consequence of the low fecundity in people with schizophrenia and other neurodevelopmental phenotypes to which these CNVs contribute, CNVs with large effects on risk are likely to be rapidly removed from the population by natural selection. Accordingly, such CNVs must frequently occur as recurrent de novo mutations. In a sample of 662 schizophrenia proband–parent trios, we found that rare de novo CNV mutations were significantly more frequent in cases (5.1% all cases, 5.5% family history negative) compared with 2.2% among 2623 controls, confirming the involvement of de novo CNVs in the pathogenesis of schizophrenia. Eight de novo CNVs occurred at four known schizophrenia loci (3q29, 15q11.2, 15q13.3 and 16p11.2). De novo CNVs of known pathogenic significance in other genomic disorders were also observed, including deletion at the TAR (thrombocytopenia absent radius) region on 1q21.1 and duplication at the WBS (Williams–Beuren syndrome) region at 7q11.23. Multiple de novos spanned genes encoding members of the DLG (discs large) family of membrane-associated guanylate kinases (MAGUKs) that are components of the postsynaptic density (PSD). Two de novos also affected EHMT1, a histone methyl transferase known to directly regulate DLG family members. Using a systems biology approach and merging novel CNV and proteomics data sets, systematic analysis of synaptic protein complexes showed that, compared with control CNVs, case de novos were significantly enriched for the PSD proteome (P=1.72 × 10−6). This was largely explained by enrichment for members of the N-methyl-D-aspartate receptor (NMDAR) (P=4.24 × 10−6) and neuronal activity-regulated cytoskeleton-associated protein (ARC) (P=3.78 × 10−8) postsynaptic signalling complexes. In an analysis of 18 492 subjects (7907 cases and 10 585 controls), case CNVs were enriched for members of the NMDAR complex (P=0.0015) but not ARC (P=0.14). Our data indicate that defects in NMDAR postsynaptic signalling and, possibly, ARC complexes, which are known to be important in synaptic plasticity and cognition, play a significant role in the pathogenesis of schizophrenia.

VACTERL-H syndrome: first trimester diagnosis

We present two consecutive female fetuses with identical upper limb anomalies. The first of the cases was found to have ventriculomegaly, atrial septal defect, anal atresia, narrowing of the duodenal lumen and unilateral renal agenesis at the end of the second trimester. These abnormalities were characteristic of autosomal recessive VACTERL-H syndrome. The second case was diagnosed to have absent radii and thumbs at 11 weeks. Detailed examination of fetal limbs in the first trimester screening in cases with high risk is useful for early detection of this malformation.

X‐linked VACTERL with hydrocephalus syndrome: Further delineation of the phenotype caused by FANCB mutations

X-linked VACTERL-hydrocephalus syndrome (X-linked VACTERL-H) is a rare disorder caused by mutations in the gene FANCB which underlies Fanconi Anemia (FA) complementation group B. Cells from affected males have increased chromosome breakage on exposure to DNA cross-linking agents. Only five FANCB mutations found in six affected males, including an affected uncle and nephew, have been reported. We have identified FANCB mutations in a further four affected families. The VACTERL-H phenotype segregates as an X-linked recessive trait in three of these. Each mutation is predicted to truncate the FANCB open reading frame and results in highly skewed X-inactivation in unaffected carrier females. Phenotypic data were available on six affected males. Comparison of the clinical findings in our patients with published clinical data (total 12 patients) shows that ventriculomegaly, bilateral absent thumbs and radii, vertebral defects, renal agenesis, and growth retardation are the major phenotypic signs in affected males. Less frequent are brain, pituitary, ear and eye malformations, gastrointestinal atresias (esophageal, duodenal and anal), tracheoesophageal fistula, lung segmentation defects, and small genitalia. Three of six of our patients survived the perinatal period. One boy lived up to 2 years 10 months but developed aplastic anemia and died of renal failure. These data show that loss-of-function FANCB mutations result in a recognizable, multiple malformation phenotype in hemizygous males for which we propose clinical criteria to aid diagnosis.

Thrombocytopenia-Absent Radius Syndrome

Thrombocytopenia-absent radius (TAR) syndrome is a relatively uncommon condition characterized by absent radii with the presence of thumbs and congenital or early-onset thrombocytopenia that tends to resolve in childhood. The precise cause of this condition is unknown, although recently a microdeletion of chromosome 1q21.1 has been found in all investigated individuals. However, this microdeletion alone is not sufficient to cause TAR syndrome, and another, uncharacterized genetic alteration is thought to be involved in the pathogenesis.

Ulnar dimelia variant: a case report

We report a case of ulnar dimelia, commonly called mirror hand, in a 2-month-old female child who had restriction of elbow flexion and forearm rotation. There was no facial or other internal organ malformation. Radiographs revealed seven triphalangeal digits with double ulnae (one following the other) and absent radius. To the best of the authors’ knowledge, this is the first report of this mirror hand deformity in which fingers are symmetrical while duplicated ulnae are not.

Exacerbation of thrombocytopenia in a pregnant woman with thrombocytopenia–absent radius syndrome

degreeof dysfunction [4]. It is uncertainwhethermisoprostol is removed via dialysis [4]. Thus, its use for medical abortion in women with renal disease has been a point of contention, with most obstetricians opting against use. However, in the present cases, misoprostol was used to achieve abortion in consenting women with impaired renal function, with no adverse effects. Larger studies are required to determine the optimum doses at different degrees of renal impairment.

Developmental differences in megakaryocytopoiesis are associated with up-regulated TPO signaling through mTOR and elevated GATA-1 levels in neonatal megakaryocytes

AbstractMultiple observations support the existence of developmental differences in megakaryocytopoiesis. We have previously shown that neonatal megakaryocyte (MK) progenitors are hyperproliferative and give rise to MKs smaller and of lower ploidy than adult MKs. Based on these characteristics, neonatal MKs have been considered immature. The molecular mechanisms underlying these differences are unclear, but contribute to the pathogenesis of disorders of neonatal megakaryocytopoiesis. In the present study, we demonstrate that low-ploidy neonatal MKs, contrary to traditional belief, are more mature than adult low-ploidy MKs. These mature MKs are generated at a 10-fold higher rate than adult MKs, and result from a developmental uncoupling of proliferation, polyploidization, and terminal differentiation. This pattern is associated with up-regulated thrombopoietin (TPO) signaling through mammalian target of rapamycin (mTOR) and elevated levels of full-length GATA-1 and its targets. Blocking of mTOR with rapamycin suppressed the maturation of neonatal MKs without affecting ploidy, in contrast to the synchronous inhibition of polyploidization and cytoplasmic maturation in adult MKs. We propose that these mechanisms allow fetuses/neonates to populate their rapidly expanding bone marrow and intravascular spaces while maintaining normal platelet counts, but also set the stage for disorders restricted to fetal/neonatal MK progenitors, including the Down syndrome–transient myeloproliferative disorder and the thrombocytopenia absent radius syndrome.