TAR syndrome

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. This syndrome may occur as a part of the 1q21.1 deletion syndrome

Presentation
Symptoms of thrombocytopenia, or a lowered platelet count, leads to bruising and potentially life-threatening hemorrhage.

Other common links between people with TAR seem to include heart problems, kidney problems, knee joint problems, frequently lactose intolerance and often thumb hypoplasia



Treatment
Treatments range from platelet transfusions to surgery 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 year of life. For most people with TAR, platelet counts improve as they grow out of childhood.

Genetics
Genetic research is underway. 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, so there are likely other genetic components of the syndrome besides this one, hence when a child has the condition any future siblings are likely to have a 25% chance of also having it.

Epidemiology
The incidence is 0.42 per 100,000 live births.

History
TAR was first identified in 1956, and was named almost thirteen years later when severe bruising (along with abnormally short forearms) was present in three families with nine newborns.