Genetic Basis and Clinical Implications of Thrombocytopenia-Abscent Radius Syndrome

Thrombocytopenia-absent radius (TAR) syndrome is a rare autosomal recessive disorder characterised by a combination of bilateral radial bone aplasia with preserved thumbs and early‐onset thrombocytopenia. Its genetic basis lies in compound heterozygosity for a microdeletion on chromosome 1q21.1 and a low‐frequency, non-coding variant in the RBM8A gene, which together lead to reduced expression of the Y14 protein and dysregulation of megakaryopoiesis. The resulting platelet deficiency often manifests within weeks of birth, with risks of haemorrhage that may improve over the first two years of life as residual megakaryocyte function recovers. Skeletal findings are constant, whereas additional anomalies—cardiac, renal, gastrointestinal and urological—occur variably, underscoring the need for multidisciplinary care. Clinically, management centres on early diagnosis through targeted genetic testing, supportive platelet transfusions during bleeding episodes, and vigilant surveillance for associated malformations. Emerging insights into the molecular mechanisms have opened avenues for novel therapies, including the potential use of thrombopoietin receptor agonists, and emphasise the importance of family counselling and prenatal screening. Globally, improved understanding of TAR syndrome informs best practice guidelines, shaping patient outcomes and directing future research into genotype–phenotype correlations.

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Genetic Basis and Clinical Implications of Thrombocytopenia-Abscent Radius Syndrome publication trend

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Technical terms

Compound heterozygosity: Inheritance of two different pathogenic alleles at a single gene locus.

Hypomorphic allele: A variant that reduces but does not eliminate gene function.

Microdeletion: A chromosomal deletion of a small genomic segment, often involving multiple genes.

Megakaryopoiesis: The process by which bone marrow progenitors differentiate into platelet‐producing megakaryocytes.

RBM8A: Gene encoding the Y14 protein, a component of the exon–junction complex crucial for RNA processing.

References

1. Thrombocytopenia-Absent Radius Syndrome: Descriptions of Three New Cases and a Novel Splicing Variant in RBM8A That Expands the Spectrum of Null Alleles. International Journal of Molecular Sciences (2022).
2. Thrombocytopenia-absent radius (TAR) syndrome due to compound inheritance for a 1q21.1 microdeletion and a low-frequency noncoding RBM8A SNP: a new familial case. Molecular Cytogenetics (2015).
3. Thrombocytopenia with absent radii syndrome with delayed presentation of thrombocytopenic episodes: a case report. Annals of Medicine and Surgery (2023).
4. Thrombocytopenia With Absent Radii Syndrome With an Unusual Urological Pathology: A Case Report. Cureus (2022).