Molecular diagnosis of thrombocytopenia‐absent radius syndrome using next‐generation sequencing

Summary Introduction Thrombocytopenia‐absent radius ( TAR ) syndrome is a rare autosomal recessive disease. Patients are compound heterozygotes for a loss‐of‐function allele, which in most cases is a large genomic deletion on chromosome 1q21.1 containing the RBM 8A gene, and a noncoding variant located in the 5′ UTR (rs139428292) or intronic (rs201779890) regions of RBM 8A . As the molecular genetic testing in TAR requires multiple techniques for detection of copy‐number variations ( CNV ) and nucleotide substitutions, we tested whether a next‐generation sequencing ( NGS ) approach could identify both alterations. Methods Two unrelated families were analyzed with Ion PGM sequencing using a target panel of genes responsible for different forms of inherited thrombocytopenia. A statistical quantitative evaluation of amplicon coverage was performed to detect CNV , in particular those on the RBM 8A gene. Results All the probands were apparently homozygous for the rare allele inherited by the father at the rs139428292 locus, suggesting the presence of a deletion on the maternal chromosome. The statistical analysis confirmed the hemizygous condition of RBM 8A . Conclusion We concluded that NGS approaches could be used as a cost‐effective method for molecular investigation of TAR as they could simultaneously detect CNV and point mutations.