Bleeding Gums and Rash on Both Legs in a 38-Year-Old Man

Discussion

Primary immune thrombocytopenia, also known as idiopathic or immune thrombocytopenic purpura (ITP), is an acquired thrombocytopenia possibly caused by autoantibodies directed against platelet antigens.^[1] It is defined as isolated thrombocytopenia (platelet count < 100,000/µL) without anemia, leukopenia, or any other cause of thrombocytopenia; thus, it is a diagnosis of exclusion. ITP is considered a common acquired bleeding disorder. It is often a chronic condition in adults, and prevalence therefore exceeds incidence. Prevalence is estimated to be approximately eight cases per 100,000 children and 12 cases per 100,000 adults in the United States.^[1] Distinguishing ITP from other causes of thrombocytopenia that may present in a similar fashion is important, as is determining whether ITP is primary or secondary to an underlying medical condition, as this can affect management.

Primary ITP accounts for most cases, and a presumptive diagnosis of primary ITP is made when the history, physical examination, and laboratory testing excludes all other causes of thrombocytopenia. Secondary ITP is diagnosed in a patient with ITP and an underlying condition that can mediate it, such as HIV infection, hepatitis C virus (HCV) infection, systemic lupus erythematosus (SLE), and chronic lymphocytic leukemia. Drugs can also cause secondary ITP or drug-induced immune thrombocytopenia. Commonly implicated drugs include beta-lactam antibiotics, trimethoprim-sulfamethoxazole, phenytoin, quinine, quinidine, and carbamazepine.

The pathogenesis of ITP is still incompletely understood. The underlying mechanism for the reduced platelet lifespan may be secondary to the presence of antibody-mediated destruction of platelets.^[1,2] Specifically, the production of immunoglobulin G autoantibodies by B cells directed against platelet membrane glycoproteins (such as IIb/IIIa) may be responsible.^[1,2,3] In some patients an inciting event is present, such as a preceding viral infection or, less commonly, a bacterial infection that triggers the production of these antibodies. These antibodies then cross-react with normal platelet antigens, causing destruction of platelets.

Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this: Basma Abdulhadi. Emergency Medicine Case Challenge: Bleeding Gums and Rash on Both Legs in a 38-Year-Old Man - Medscape - Apr 12, 2023.

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