Platelet Abnormalities

Platelet abnormalities can be categorized as either disorder of dysfunction (for which transfusion therapy may be futile) or disorders of quantity (for which transfusion is beneficial).

1. Decreased platelet production may be seen in patients with marrow dysfunction caused by infiltration, infection, drugs, or radiation.

2. Increased platelet destruction is seen in patients with idiopathic thrombocytopenic purpura or TTP, hemolytic–uremic syndrome, DIC, or viral infections.

3. Splenic sequestration of platelets can occur in hypothermic patients or those with hypersplenism (e.g., with portal hypertension).

4. Platelet loss can be seen with hemorrhage or hemodialysis.

5. Thrombocytosis, seen in patients with polycythemia vera, splenectomy, or malignancy, may result in coagulopathy when platelet counts exceed 1 million/mm3.

CLINICAL FINDINGS

1. Asymptomatic: Incidental thrombocytopenia may be found by laboratory testing in asymptomatic patients.

2. Hemorrhage: Patients with significant platelet dysfunction may have some form of mucocutaneous hemorrhage, and extreme platelet disease may result in catastrophic cerebrovascular hemorrhage.

— The presence of petechiae, ecchymosis, or purpura may provide clues to the presence of thrombocytopenia.

— Mucocutaneous bleeding is suspicious for platelet abnormality.

3. Splenomegaly: The finding of splenomegaly on abdominal examination may help define the cause.

EVALUATION: Laboratory assessment includes a hematocrit, platelet count, and coagulation profile. Measurement of the bleeding time to assess platelet function is usually performed in a specialized laboratory. The bleeding time usually becomes abnormal with platelet counts lower than 50,000/mm3 (normal counts range from 150,000 to 450,000/mm3).

THERAPY

1. Platelet administration is indicated for all patients with platelet levels below 10,000/mm3 and many patients with platelet levels below 50,000/mm3. Administration of platelets may be counterproductive in some patients with the hematologic disease (e.g., TTP). Consultation should be obtained before transfusing platelets in such patients.

2. Other therapies are necessary when thrombocytopenia is caused by platelet destruction. Prednisone is often indicated for patients with TTP, idiopathic thrombocytopenic purpura, or hemolytic–uremic syndrome.