(Science: syndrome) tar stands for thrombocytopenia (low blood platelets) and aplasia (absence) of the radius (the long bone on the thumb-side of the forearm), features characterizing this syndrome. There is phocomelia (flipper-limb) with the thumbs always present. The fibula (the smaller bone in the lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the tar child. Alternative names include thrombocytopenia-absent radius syndrome, radial aplasia-thrombocytopenia syndrome, and tetraphocomelia-thrombocytopenia syndrome.