A chromosomal deletion syndrome that is characterized by absence of the radius bone and platelet deficiency and bilateral absence of the radii with the presence of both thumbs and generally transient thrombocytopenia (less than 50 platelets/nL) and that has_material_basis_in compound heterozygosity for a rare null mutation involving the RBM8A gene on chromosome 1q12 on 1 allele and 1 of 2 low-frequency noncoding single-nucleotide polymorphisms in RBM8A on the other.