Prenatal diagnosis of thrombocytopenia-absent-radius (TAR) syndrome

Thrombocytopenia Absent Radius (TAR)-Syndrome: From Current Genetics to Patient Self-Empowerment

Thrombocytopenia absent radius (TAR) syndrome is a rare form of hereditary thrombocytopenia associated with a bilateral radial aplasia. TAR syndrome is genetically defined by the combination of a microdeletion on chromosome 1 which includes the gene RBM8A, and a single nucleotide polymorphism (SNP) in the second RBM8A allele. While most patients with TAR syndrome harbor a SNP in either the 5' UTR region or in intron 1 of RBM8A, further SNPs associated with TAR syndrome are still being identified. Here, we report on the current understanding of the genetic basis, diagnosis, and therapy of TAR syndrome and discuss patient self-empowerment by enabling networking and exchange between affected individuals and families.

Fetal cardiac abnormalities: Genetic etiologies to be considered

Congenital heart diseases are a common prenatal finding. The prenatal identification of an associated genetic syndrome or a major extracardiac anomaly helps to understand the etiopathogenic diagnosis. Besides, it also assesses the prognosis, management, and familial recurrence risk while strongly influences parental decision to choose termination of pregnancy or postnatal care. This review article describes the most common genetic diagnoses associated with a prenatal finding of a congenital heart disease and a suggested diagnostic process.

Thrombocytopenia with Unilateral Dysplastic Radius- Is it Thrombocytopenia - Absent Radius (TAR) Syndrome?

Thrombocytopenia - absent radii (TAR) syndrome is an autosomal recessive genetic rare disorder with hypomegakaryocytic thrombocytopenia and bilateral absent radius that may have additional anomalies. This disorder is characterized by thrombocytopenia resulting in potentially severe bleeding episodes primarily during infancy. We report the case of a 7-day-old term appropriate for gestational age (AGA) male baby, product of non consanguineous marriage presented with bloody loose stool, right sided upper limb deformity and paleness of the body, was diagnosed as TAR syndrome with some atypical presentation. Such type of atypical presentation has not been previously reported in a case with TAR Syndrome.Patient was managed in our hospital with packed cell transfusion and two units platelets concentrates transfusion, Intra-venous antimicrobials, and other supportive treatment. He gradually improved and was discharged after seven days of hospital stay with advice to consult orthopedic surgeon for opinion regarding limb reconstruction.

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

Background

Thrombocytopenia–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 age

Case presentation

We 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, respectively

Conclusion

The 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.

Prenatal diagnosis of thrombocytopenia-absent radius syndrome

The prenatal diagnosis of thrombocytopenia-absent radius (TAR) syndrome by ultrasound is established. The sonographic findings showed bilateral absence of the radii and club hands with normal thumbs and metacarpals. Thrombocytopenia was identified from the postabortal cord blood. Three-dimensional computerized tomography images confirmed the sonographic diagnosis. This report, to our knowledge, is one of the few cases published in the literature about the prenatal diagnosis of TAR syndrome.

Prenatal identification of isolated bilateral radial dysplasia

Radial aplasia or hypoplasia is characterized by complete or partial absence of the radius and/or radial ray structure occurring in 1:30,000 live births. It may be unilateral or bilateral of varying severity, and may be isolated or associated with other anomalies. We report an unusual case of isolated radial aplasia at 20 weeks' gestation with complete absence of the right radius and thumb associated with marked hypoplasia of the left radius. The intrauterine 2- and 3-dimensional findings, postnatal radiographic evaluation, and autopsy results are reported.

A clinical algorithm of prenatal diagnosis of Radial Ray Defects with two and three dimensional ultrasound

OBJECTIVE

To review the antenatal diagnosis of Radial Ray Defects (RRD) in a tertiary referral fetal medicine unit & to set out a clinical algorithm to aid assessment and management.

METHODS

All cases of RRD isolated or associated with other anomalies notified to NorCAS between 2000 and 2005 were identified. Outcome information was obtained from paediatric records and histopathology and cytogenetics in cases of pregnancy interruption.

RESULTS

Thirty five cases were referred, 17 cases were excluded including skeletal dysplasia (16). An antenatal diagnosis was made in 61% (11/18) - isolated limb reduction defects, Trisomy 18, TAR, fetal valproate syndrome, Roberts syndrome. Of the rest, 3 had a cordocentesis with normal chromosome fragility tests (VACTERL association, Goldenhar syndrome and Acrofacial dysostosis) and 4 declined testing (2 TOP with Cornelia de Lange, 2 ongoing pregnancies diagnosed postpartum with Fanconi anaemia and VACTERL association).

CONCLUSIONS

The challenge of radial ray anomalies is to combine clinical and ultrasound expertise with input from clinical genetics, ultrasound and molecular testing. Our clinical algorithm encourages targeted sonography including 3D views for subtle face, ear and hand anomalies, providing a useful tool to diagnose the underlying condition, crucial for appropriate obstetric management and prognosticating for future pregnancies.

An unusual association of TAR syndrome with esophageal atresia: a variant?

Thrombocytopenia and absent radii (TAR) syndrome is a rare disorder. It may be associated with, for example, as cardiovascular, genitourinary, gastrointestinal, skeletal, neurological, ophthalmic, and facial anomalies. Esophageal atresia is also a rare anomaly associated with genitourinary, skeletal, and cardiovascular anomalies, among others. Here, the authors present a child with TAR syndrome and esophageal atresia with tracheoesophageal fistula. This association has been reported in only one other case in literature.

Mullerian Agenesis and Thrombocytopenia Absent Radius Syndrome: A Case Report and Review of Syndromes Associated With Mullerian Agenesis

Mullerian agenesis, commonly referred to as Mayer-Rokitansky-Kuster-Hauser syndrome (MRKHS), is a congenital defect that is most commonly associated with renal and spinal malformations. It is very rare for Mullerian agenesis to be accompanied by malformations of the extremities. In this report, we describe a 22-year-old woman with Mullerian agenesis and thrombocytopenia absent radius syndrome (TARS). We also review rare syndromes associated with Mullerian anomalies, including Mullerian hypoplasia/aplasia-renal agenesis-cervicothoracic somite dysplasia (MURCS), Roberts syndrome, Bardet-Biedl syndrome (BBS), McKusick-Kaufman syndrome (MKS), Wolf-Hirschhorn syndrome, and others. The pathogenesis of these complex malformation syndromes is not well understood as a result of their sporadic occurrence. However, some of these syndromes do follow a pattern of inheritance, suggesting that they could provide insights into our understanding of their origins.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to review the rare congenital defects associated with Mullerian agenesis, to determine the genetic etiologies of the associated syndromes with Mullerian agenesis, and to discuss information for parental counseling related to inheritance patterns and growth and development of the affected child.

Fetal cardiac anomalies and genetic syndromes

Cardiac anomalies may occur in isolation or can be part of a genetic syndrome. In this article, we describe some of the genetic syndromes commonly associated with cardiac anomalies where there are other sonographic features that may aid accurate prenatal diagnosis.