Thrombocytopenia-Absent Radius Syndrome Workup

Updated: May 09, 2016
  • Author: John K Wu, MBBS, MSc, FRCPC; Chief Editor: Hassan M Yaish, MD  more...
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Workup

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.

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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.

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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
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Procedures

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. [19] The infant was delivered within 24 hours of the transfusion with no complications.

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