A 25-year-old woman comes to the office due to heavy menses. Over the past few months, the patient's menstrual periods have lasted 7 days rather than the usual 3 days. In addition, her menstruation has been unusually heavy and has, at times, bled through her clothing while at work. The patient is an active volleyball player but has not been able to play recently due to increasing fatigue; frequent, diffuse myalgias; and bilateral pain in her wrists that requires icing after practice. She has also noticed that her forearms become easily bruised in areas where the ball hits. The patient takes no medications and does not use tobacco, alcohol, or illicit drugs. Temperature is 37 C (98.6 F), blood pressure is 116/76 mm Hg, pulse is 76/min, and respirations are 16/min. There are scattered petechiae across the body with a few large ecchymoses on the forearms. The remainder of the physical examination is normal. Laboratory results are as follows:
| Complete blood count | |
| Hematocrit | 37% |
| Platelets | 24,000/mm3 |
| Leukocytes | 11,000/mm3 |
| Coagulation studies | |
| PT | 12 sec |
| Activated PTT | 38 sec |
Peripheral blood smear shows normal and large platelets. Which of the following is the best next step in evaluation of this patient?
Immune thrombocytopenic purpura | |
Epidemiology |
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Manifestations |
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Diagnosis |
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Treatment |
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CLL = chronic lymphocytic leukemia; HCV = hepatitis C virus; ITP = immune thrombocytopenic purpura; IVIG = intravenous immunoglobulin. | |
Immune thrombocytopenia (ITP) is an acquired disorder marked by the formation of autoantibodies to platelet surface glycoproteins, which increases platelet clearance in the spleen and inhibits megakaryocytosis. In ITP, platelet counts fall to <100,000/mm3, leading to prolonged skin/mucosal bleeding (eg, menstrual, nasal), ecchymosis, and petechiae.
ITP is a diagnosis of exclusion; therefore, other causes of thrombocytopenia (eg, drug-induced thrombocytopenia, liver disease, hypersplenism, microangiopathic disorders, bone marrow abnormalities) must be ruled out. In ITP, leukocyte count, erythrocyte count, and coagulation studies are normal; peripheral blood smear usually shows normal platelet morphology (both normal-sized and large platelets may be seen due to increased platelet turnover).
ITP is categorized as either primary (no discernible cause) or secondary (due to an underlying condition). HIV and hepatitis C are the most common secondary causes, so testing for these 2 conditions is generally performed. Additional testing is warranted when specific signs or symptoms of another disorder are present. This patient's myalgias and arthralgias raise concern for an autoimmune disease (eg, systemic lupus erythematosus); therefore, antinuclear antibody testing is advisable.
(Choice B) Ascorbic acid (vitamin C) deficiency causes impaired collagen synthesis and can lead to ecchymosis and palpable purpura. However, most cases occur in severely malnourished individuals or those who use alcohol or illicit drugs.
(Choice C) Factor VIII deficiency can cause similar bleeding symptoms but is associated with prolonged PTT. Hemophilia A, an X-linked disorder (seen only in males), causes severe factor VIII deficiency.
(Choice D) Hemoglobin electrophoresis is used to diagnose thalassemia, a genetic hemoglobin disorder associated with anemia, microcytosis, and target cells. Hemoglobin disorders do not usually cause thrombocytopenia.
(Choice E) Platelet aggregation testing evaluates for rare disorders of platelet function and is generally indicated in those who have normal platelet count and prolonged bleeding times. This patient's thrombocytopenia makes ITP far more likely; platelet aggregation testing would not be indicated.
(Choice F) Von Willebrand disease (vWD) is associated with impaired platelet aggregation, which occasionally causes bruising and prolonged mucosal bleeding. However, platelet count and PT are normal; PTT is sometimes prolonged due to increased destruction of factor VIII.
Educational objective:
Immune thrombocytopenia (ITP) is an autoimmune disorder associated with isolated thrombocytopenia. Although most cases are primary, a minority of individuals have ITP due to an underlying condition (eg, HIV, hepatitis C). Testing for HIV and hepatitis C virus is recommended for all patients with ITP; additional testing is needed when signs and symptoms of other disorders (eg, systemic lupus erythematosus) are present.