Thrombocytopenia Flashcards
What is thrombocytopenia?
Low platelets
What are the three underlying causes of thrombocytopenia?
Underproduction
Destruction
Sequestration
What is the normal ranges of platelets?
150-450k
How big are platelets relative to RBCs?
1/3 size
What is the cell that produces platelets?
Megakaryocytes
What is the chemical that determines the rate and amount of platelet production?
Thrombopoietin
What are the receptors on platelets that binds to vWF, and serves as an intracellular signal?
Gp IIb/IIIa
Stocking distribution of paresthesias with low pancytopenia =?
Pernicious anemia
Where are platelets sequestered, generally?
Spleen
What are the viral causes of thrombocytopenia? (2)
HIV
Parvo B19
Pts with sickle cell disease are susceptible to what viral infections?
Parvovirus B19
What are the two common causes of thrombocytopenia that fall under the medication/drug category?
EtOH
Chemotherapeutic agents
What are the three causes of marrow replacement that causes thrombocytopenia?
Granulomatous disease
Myelofibrosis
Malignancies
If the MCV is greater than 115, what is the disease?
megaloblastic anemia
What are the two platelet dysfunctions with pernicious anemia?
Diminished platelet aggregation
Decreased release of ATP, ADP
Elevated methylmalonic acid levels = ?
Pernicious anemia
What are the tests to diagnose pernicious anemia? (3)
Anti-parietal cell
Anti IF
EGD
What is the treatment for pernicious anemia?
SQ B12 replacement (can’t give PO d/t lack of IF)
Why is an EGD indicated for pernicious anemia?
Gastric adenocarcinoma
What is pseudothrombocytopenia?
Platelet aggregation or clumping in the test tube (in vitro)
What is the solution to pseudothrombocytopenia?
Use a blue top tube with heparinized blood
thrombocytopenia with o/w normal CBC + bleeding from gums + mucocutaneous petechial rash = ?
ITP (immune thrombocytopenia purpura)
What is ITP?
Accelerated destruction of platelets by immune destruction
How do you diagnose ITP?
Diagnosis of exclusion
What are the results of a bone marrow biopsy with ITP?
Normal to increased number of megakaryocytes
The incidence of ITP increases or decreases with age
Increases
What are the antiplatelet abs that are involved in ITP targeted against?
IgG to GPII/IIIa receptor
True or false: transfusions to pts with ITP still result in destruction of platelets
True
What are the usual symptoms of ITP?
Purpura/petechiae
Epistaxis/bleeding gums
Menorrhagia
What is the first line of drug treatment for ITP? Second? Third?
IV corticosteroids
IVIG
Rituximab
What is the last resort for ITP treatment?
Splenectomy
What is antiphospholipid antibody syndrome?
Abs to GPIIa/IIIb
Is HUS/TTP immune mediated?
no
HELLP syndrome is indicated by what? (3)
Low platelet
HTN
elevated LFTs
HIT is caused by what?
Immune mediated destruction of platelets after exposure to heparin
What do abs in HIT attach to?
heparin and PF4 complex
What type of heparin has a lower risk of HIT?
Low molecular weight heparin
What happens to HIT pts when they are left untreated?
Thromboses form
How do you manage HIT?
Stop heparin
Change anticoag
True or false: you can administer heparin in pts who have had HIT before?
True, but needs to be more than 6 months
Jaundice everywhere but the sclera is what?
NOT hyperbilirubinemia–Hyperbetacarontenamia
Thrombocytopenia d/t to sequestration generally results in what PE findings?
Splenomegaly
What are the four causes of splenic sequestration?
1/ Hereditary spherocytosis
- CML
- Hairy cell leukemia
- MALT lymphoma
True or false: DM is a common cause of liver cirrhosis
True
What are the three components of thrombocytopenia?
- Careful H&P
- Lab eval
- Bone marrow biopsy
What are the three things to look for in a PE of thrombocytopenia?
Mucocutaneous exam
Lymphadenopathy
Splenomegaly
What are the two diseases that contraindicate platelet transfusion? Why?
ITP
HIT
May accelerate platelet destruction
For every unit of blood, how much increase in platelets should you expect?
5k
What are the three things that should be a part of a PE for pts with thromboytopenia?
Mucocutaneous
Lymph
Spleen
When is a bone marrow biopsy indicated?
2 or more cell lines affected
What is the more common cause of underproduction thrombocytopenia?
Drugs
What is the tube that should be used to r/o pseudothrombocytopenia?
Blue top
