Thrombocytopenia-Absent Radius Syndrome Workup

Updated: Mar 07, 2019
  • Author: John K Wu, MBBS, MSc, FRCPC; Chief Editor: Hassan M Yaish, MD  more...
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Laboratory Studies

CBC count

The platelet count is frequently less than 50 X 109/L ( 15-30 X 109/L.) Platelet morphology looks normal on blood smear examination. Large platelets are not a feature.  Eosinophilia is observed in 50% of patients.

Leukocytosis may be present, with a WBC count >35 X 109/L with a left shift and picture of leukemoid reaction.

Anemia may be present secondary to bleeding.

Genetic findings

Chromosomes are normal. Findings on chromosomal breakage studies with clastogenic agents are normal.


Imaging Studies

Characteristic skeletal involvement (ie, absent radii) is detectable during prenatal transvaginal ultrasonography as early as 13 weeks' gestation, when sufficient fetal skeletal ossification is present.

Upper-limb abnormalities on prenatal sonograms suggest numerous syndromes in the differential diagnosis.

After radial aplasia is observed, ultrasonography of the extremities, face, and kidneys is indicated.


Other Tests

Sampling of the bone marrow (which is not required to make the diagnosis) reveals the following findings:

  • Normal or hypercellular bone marrow

  • Decreased, absent, or immature megakaryocytes

  • Small, basophilic, vacuolated megakaryocytes

  • Erythroid hyperplasia



Cordocentesis can be performed to confirm known genetic conditions. Cordocentesis poses a 1-2% risk of fetal loss and a risk of prolonged bleeding from the umbilical puncture site.

Weinblatt and associates performed in utero platelet transfusion of a fetus with radial aplasia at 37 weeks' gestation after cordocentesis revealed a platelet count of 40 X 109/L. [22] The infant was delivered within 24 hours of the transfusion with no complications.