Disseminated intravascular coagulation, 286.6
Heparin-induced thrombocytopenia, 287.4
Idiopathic Thrombocytopenic Purpura, 287.3
I. Definition
A. Disorder in which antibody-sensitive platelets are destroyed by the spleen
B. Autoimmune disorder in which immunoglobulin (Ig)G autoantibody binds to platelets, facilitating their destruction by the spleen
II. Incidence/predisposing factors
A. In children
1. Usually precipitated by a viral illness
2. Self-limiting
3. Results in bruising and mucosal bleeding
B. In adults
1. Usually chronic
2. Requires periodic treatment
C. Disease of young persons: Women ages 20 to 40 outnumber men 2:1.
D. Spontaneous recovery occurs in only 5% of adult cases.
E. Thrombocytopenia may be induced by
1. Heparin (most common cause in hospitalized patients)
2. Sulfonamides
3. Thiazides
4. Quinine
5. Cimetidine
6. Gold
F. Thrombocytopenic purpura is a common secondary manifestation of
1. Systemic lupus erythematosus (SLE) in 14% to 26% of patients
2. Chronic lymphocytic leukemia (CLL)
H. Thirteen thousand new cases of adult ITP are believed to occur each year in the U.S.
III. Subjective findings
A. Presenting complaint is usually mucosal or epidermal bleeding.
1. Epistaxis
2. Oral bleeding
3. Menorrhagia
4. Purpura
5. Petechiae
B. Patient is usually systemically well.
IV. Physical examination findings
A. Patient is afebrile and usually appears well, with no abnormal findings on examination except those related to bleeding.
B. Spleen is nonpalpable.
V. Laboratory/diagnostic findings
A. Thrombocytopenia is the hallmark of the disease; may be fewer than 10,000 platelets per microliter.
B. No definitive test for ITP exists; diagnosis occurs by exclusion.
C. Other hematopoietic cell lines are normal, although platelets are enlarged (megathrombocytes).
D. Ten percent of patients have coexistent autoimmune hemolytic anemia (Evans’ syndrome).
1. Anemia, reticulocytosis, and spherocytes are seen on peripheral smear.
2. No fragmented cells (schistocytes) should be seen.
E. Antinuclear antibody (ANA) testing may point to an autoimmune process.
F. Consider ordering the following:
1. Monoclonal antibody immobilization of platelet antigens (MAIPA)
a. Considered the most sensitive and specific antibody test
b. IgG platelet antibodies are present in 90% of patients.
2. Bone marrow biopsy (normal or increased megakaryocytes) to exclude myelodysplasia
3. All patients with decreased platelet counts should have the peripheral blood smear reviewed to confirm the automated count and to rule out ethylenediaminetetra-acetic acid (EDTA) artifact from the test.
a. Platelet clumping may be seen in a purple-top tube with EDTA.
b. Platelet count should be repeated with a blue-top tube with sodium citrate or a green-top tube with heparin.
4. WinRho, also called anti-D antibody therapy, consists of concentrated antibodies that bind to the Rh antigen on red blood cells. It works only in Rh-positive individuals born to Rh-negative mothers. It helps increase platelet count but may cause anemia. Determine blood type, specifically Rh status, if WinRho treatment (described subsequently, under VI. Management) is considered as a treatment option.
HEPARIN-INDUCED THROMBOCYTOPENIA (HIT)
I. Definition
A. Thrombocytopenia induced by heparin
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