Review Question - QID 212440

This patient’s petechial rash (flat, red, non-blanching lesions) following a viral infection and low platelet count suggest immune thrombocytopenic purpura (ITP). It is caused by the formation of IgG antibodies directed against platelet membrane glycoproteins such as GPIIb/IIIa.

ITP is a common acquired bleeding disorder that can be primary or secondary to viral infections, autoimmune disorders, malignancy, or drug reactions. Many patients are asymptomatic. For those who do have symptoms, these include petechiae, purpura, epistaxis, and rarely hemorrhages. Laboratory studies will demonstrate an isolated decrease in platelet count, which leads to an increase in bleeding time. Bone marrow biopsy will demonstrate an increase in megakaryocytes.

Figure A demonstrates petechial rash of the legs.

Incorrect Answers:
Answer 1: Antibodies against double-stranded DNA are found in systemic lupus erythematous (SLE), which usually presents with fever, joint pain, and rashes. Although this patient has an oral ulcer, her lack of other symptoms and her negative anti-nuclear antibody make SLE less likely.

Answer 2: Decrease in von Willebrand factor is seen in von Willebrand disease, which may present with petechiae. However, patients will have normal platelet counts.

Answer 3: Deficiency of ADAMTS13 is the pathophysiology of thrombotic thrombocytopenia purpura, which presents with neurologic and renal symptoms, fever, thrombocytopenia, and microangiopathic hemolytic anemia.

Answer 4: Formation of noncaseating granulomas is seen in sarcoidosis, which usually presents with restrictive lung disease.

Bullet Summary:
Immune thrombocytopenic purpura is due to IgG antibodies against platelet membrane glycoproteins such as GPIIb/IIIa.