1q21.1 deletion and a rare functional polymorphism in siblings with thrombocytopenia-absent radius-like phenotypes.

Thrombocytopenia-absent radii (TAR) syndrome, characterized by neonatal thrombocytopenia and bilateral radial aplasia with thumbs present, is typically caused by the inheritance of a 1q21.1 deletion and a single-nucelotide polymorphism in on the nondeleted allele. We evaluated two siblings with TAR-like dysmorphology but lacking thrombocytopenia in infancy.