Definition:

Thrombocytopenia-absent radius (TAR) syndrome is a rare autosomal recessive syndrome characterized by severe thrombocytopenia and bilateral defects in development of the radii at birth but with preservation of the thumb. Other physical abnormalities have been reported such as ulnar and humeral deformities, rib and cervical anomalies, cardiac lesions (usually septal defects), gastrointestinal and genitourinary abnormalities. Cow's milk allergy is highly prevalent in patients with TAR syndrome. TAR syndrome is caused by the compound (bi-allelic) inheritance of one of two noncoding single-nucleotide variants and a null allele in RBM8A. Clinical management is based on presentation, with platelet transfusions as required for thrombocytopenia and orthopedic intervention for functional optimization of upper limbs.