Thrombocytopenia and absent radius (TAR) syndrome.

Abstract

Thrombocytopenia and absent radius (TAR) has become recognised as a relatively common congeni- tal anomaly syndrome characterised by hypomegakaryocytic thrombocytopenia (less than 100 000 platelets per mm3) and bilateral absence of the radius with an autosomal recessive pattern of inheritance. Initially the condition was considered to be a form of Fanconi's anaemia; however, by 1969 a total of 40 cases had been reported and it could be distinguished as a specific entity with a quite different natural history from Fanconi's anaemia.1 Subsequently, more than a hundred cases have been published from all over the world representing a broad spectrum of ethnic groups. A variety of interesting hypotheses has been made, but the pathogenic mechanisms producing the syndrome are still not understood. The clinical features of TAR include haematological abnormalities (of platelets, white cells, and possibly red cells), skeletal abnor- malities (primarily of both arms and legs), cardiac abnormalities (particularly tetralogy of Fallot and atrial septal defects), and cow's milk allergy or intolerance (leading to gastrointestinal disturb- ance in the first few years of life). A number of other unusual features have been described.