Melanie R. Drake, MD

ABSTRACT: A scheme-based approach, supported by a simple mnemonic, can narrow the broad differential diagnosis of thrombocytopenia. This approach uses findings from the complete blood cell count and the peripheral smear to organize the possible causes of thrombocytopenia into those that affect only platelet count, those that produce both a low platelet count and hemolytic anemia, and those that produce disturbances in all 3 blood cell lines. Causes of isolated thrombocytopenia include viral infections, immune-mediated platelet destruction, congenital diseases, gestational thrombocytopenia, conditions in which splenomegaly is a prominent feature, antiphospholipid antibody syndrome, infectious diseases of bacterial origin, and drugs. Causes of thrombocytopenia in conjunction with hemolytic anemia include hemolytic uremic syndrome, thrombotic thrombocytopenia purpura, and disseminated intravascular coagulation. Disorders that produce disturbances in all 3 blood cell lines include aplastic anemia, myeloproliferative syndromes, myelodysplasia (both primary and secondary), myelofibrosis, myelophthisis, and several other diseases in which splenomegaly is prominent.

A 56-year-old woman presents for a routine examination. She has been healthy, and results of previous examinations have been normal.

Shown here are the left hands of 2 women who had been outside together on a cold Indiana afternoon.