ABSTRACT
Thrombocytopenia with absent radii (TAR) is a rare, autosomal recessive disorder that is usually diagnosed at birth as the vast majority of these patients are thrombocytopenic and have the pathognomonic physical sign of bilateral absent radii. Other skeletal abnormalities involving the ulnae, fingers and lower limbs are also seen but are much less common. TAR differs from Fanconi anemia in several ways; the absent radii are accompanied by the presence of thumbs, the thrombocytopenia is the only cytopenia, there is absence of spontaneous or clastogenic stress-induced chromosomal breakage and evolution to aplastic anemia and leukemia have not been reported.4,7
The majority of children with TAR have recurrent significant bleeding episodes in the first 6 months of life.4,7
Intracerebral and gastrointestinal hemorrhage are the usual causes of mortality with previously one in four of these children dying by 4 years of age. The majority of these deaths however, occur in the first year of life. The mainstay of treatment is judicious use of single-donor platelet concentrates aiming to keep the platelet count above 20 × 109/L, especially in the first year of life as this is the time of maximum morbidity and mortality.4,7
Amegakaryocytic thrombocytopenia (AMEGA) is an extremely rare disorder of infancy and early childhood. The thrombocytopenia is non-immune, usually severe and early bone marrow examination shows a normal karyotype, with absent or greatly reduced numbers of megakaryocytes. Platelet transfusions are the main therapeutic intervention from diagnosis.7
