Abstract

TAR Syndrome (thrombocytopenia with absent radius) is a rare genetic disorder that is characterized by the absence of the radius bone in the forearm and a dramatically reduced platelet count.

Presentation

Other common links between people with TAR seem to include anemia, heart problems, kidney problems, knee joint problems, frequently lactose intolerance.

Different cases with leukemia in patients with TAR are described in.

Genetics

A 2007 research article identified a region of chromosome 1, 1q21.1, containing 11 genes (including HFE2, LIX1L, PIAS3, ANKRD35, ITGA10, RBM8A, PEX11B, POLR3GL, TXNIP, and GNRR2), that is heterozygously deleted in thirty of thirty patients with TAR. This deletion was also found in 32% of unaffected family members, indicating that the condition requires an additional modifier.

This modifier was discoverd in 2012. A study identified two separate single-nucleotide polymorphism (SNP) in "RBM8A". These abnormalities resulting in reduced Y14 production that were responsible for all but two of the cases studied, one a 5'UTR SNP with a frequency of 3.05% and the other an intronic SNP with a frequency of 0.42% in 7504 healthy individuals of the Cambridge BioResource. The microdeletion was not found in 5919 controls of the Wellcome Trust Case Control Consortium.

Treatment

Treatments range from platelet transfusions to surgery aimed at either centralizing the hand over the ulna to improve functionality of the hand or aimed at 'normalizing' the appearance of the arm, which is much shorter and 'clubbed.' There is some controversy surrounding the role of surgery. The infant mortality rate has been curbed by new technology, including platelet transfusions, which can even be performed in utero. The critical period is the first and sometimes second year of life. For most people with TAR, platelet counts improve as they grow out of childhood.

History

In 1929 Greenwald and Sherman described the first patient with TAR Syndrome. 40 years later Hall collected 40 cases and introduced the name "Thrombocytopenia with absent radius". In 1988 Hedberg published an article with 100 cases.

The bigenetic background was described in 2007 and 2012.