Thrombocytopenia with absent radii (TAR) syndrome must be distinguished from other genetic disorders with aplasia of the radii.


Synonym: chromosome 1q21.1 deletion syndrome


Chromosome affected: 1q21.1


Defect: deletion. Minimal size 200 kb. Most common 500 kb.


Inheritance: variable with about 25% sporadic


Clinical features:

(1) bilateral absence of radii

(2) thumbs present and not hypoplastic (may be wider and flatter than normal)

(3) transient episodes of thrombocytopenia, which may be present at birth or appear during infancy

(4) cow milk allergy common; this may be associated with gastroenteritis and thrombocytopenia

(5) variable renal and female genital malformations

(6) variable cardiac malformations

(7) variable skeletal malformations (vertebrae, ribs, lower limbs, upper limbs, fingers)


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