TAR syndrome

TAR Syndrome (Thrombocytopenia with Absent radius) is a rare genetic disorder which is characterized by the absence of the radius bone in the forearm, and a dramatically reduced platelet count.

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.

A region of chromosome 1, 1q21.1, containing 11 genes, is mutated in thirty of thirty patients with TAR.^[1] This mutation 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.

Other common links between people with TAR seem to include heart problems such as secundum atrial septal defect, kidney problems, knee joint problems and frequently lactose intolerance.

The incidence is 0.42 per 100,000 live births.

The critical period is the first year of life. For most people with TAR, platelet counts improve as they grow out of childhood.

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

Treatments range from platelet transfusions through 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.

• UK support group including personal stories and medical information

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