Test 6: Platelet Disorders Flashcards
Defined as a plt. count < 1000,000/uL
less than _________ is critical
thrombocytopenia
20,000/ug (cue for transfusion)
Thrombocytopenia may result from …
- Defective production in bone marrow
- Disorders of distribution and dilution
- Destruction of platelets
What is the normal platelet count range?
150-450 x 10^9/L
What can cause defective production in the bone marrow?
- Decreased # of megakaryocytes
-congenital (Fanconi’s anemia, May-Hegglin anomaly, maternal infection) - Ineffective plt production (caused by impaired DNA synthesis
-hereditary thrombocytopenia
-Megaloblastic anemias
Different types of thrombocytopenia
-non-immune
-immune
-disorders of distribution and dilution of plt
-disorders from destruction of plt. (can result in DIC)
examples of non-immune thrombocytopenia
TTP, HUS, and DIC (aka Microangiopathic Thrombocytopenias)
What are the five types of immune thrombocytopenia?
-Idiopathic (or immune) Thrombocytopenia Purpura
-secondary autoimmune (ITP)
-drug-induced (Ex. HIT)
-post-transfusion
-neonatal alloimmune thrombocytopenias (NAIT)
Immune thrombocytopenias are associated with…
-Igs/compliment on plt. surface
OR
-production of specific anti-plt. Abs
-autoimmune bleeding disorder
-most common form of thrombocytopenia (<200,000/yr in US)
Immune (Idiopathic) Thrombocytopenic Purpura (ITP)
Characterized by deposition of Abs that bind to plt. surface (which are destroyed by phagocytosis in spleen and liver) in addition to abnormal B and T cells
Immune (Idiopathic) Thrombocytopenic Purpura (ITP)
-Acute ITP
-Chronic ITP
symptoms of both acute and chronic types of Immune (Idiopathic) Thrombocytopenic Purpura (ITP)?
-petechiae
-ecchymoses
-epitaxis
-menorrhagia
broad range of severity
In ITP, there are no real p.b. abnormalities except for decreased ___________ count.
How is diagnosis made?
platelet
by exclusion
laboratory findings with ITP include…
-increased MPV
-decreased plt. count (<100 x 10^9/uL)
-megakaryocytic hyperplasia
increased bleeding time
-plt-associated IgG
-usually rapid onset in children
-usually follows recovery from viral infection (CMV, rubella, chicken pox) or post-vaccination
-generally self-limiting (remission in 4-6 weeks)
Acute ITP
Plt. count is usually __________with acute ITP
<20,000/mm^3
Treatment for Acute ITP?
usually not needed, but intravenous immunoglobulin (IVIG), plt transfusion, and splenectomy may be needed
-usually occurs in adults (20-50y)
-three times more likely to be found in females
Chronic ITP
-slow, asymptomatic onset
-can be associated with SLE, HIV, or pregnancy-related
-fluctuating course (can last months to years)
Chronic ITP
antibodies target GP IB/IX or GP IIb/IIIa
Chronic ITP
Chronic ITP plt. range
30,000-80,000/mm3
Treatment of ITP?
depends on the severity,
-IVIG is treatment of choice
-prednisone and corticosteroids can be used
Drug-induced Thrombocytopenia can be caused by…
-quinidine/sulfonamide drugs, hapten-dependent antibodies, and drug-induced autoantibodies (>200 drugs responsible)
antibody induced by drug binds to GPIb/IX or GPIIb/IIIa
Quinidine/sulfonamide-induced thrombocytopenia
Occurs when a drug molecule is too small to react by itself, acts as a hapten, and bind to a glycoprotein to form a complex that acts as a complete antigen. Ex: penicillin
Drug-induced Thrombocytopenia:
Hapten-dependent antibodies