Primary (Platelet) Hemostatic Disorders Flashcards
(36 cards)
What are the types of primary hemostatic diseases?
Quantitative
- decreased platelet count (thrombocytopenia)
- normal platelet function
Qualitative
- decreased platelet function
- normal platelet count
What are common symptoms of primary hemostatic (platelet) disorders?
Mucosal bleeding:
- epistaxis (most common)
- menorrhagia
- hemoptysis
- hematuria
- menorrhagia
Skin bleeding:
- petechiae (1-2mm)
- purpora (>3mm)
- ecchymosis (>1cm)
What is the most common cause of thrombocytopenia?
immune thrombocytopenic purpora (ITP)
What is immune thrombocytopenic purpora (ITP)?
Autoimmune disorder; platelet specific IgG
What is the mechanism of immune thrombocytopenic purpora?
- IgG produced in the spleen opsonizes platelets
- splenic macrophages eat the platelets -> thrombocytopenia
What lab findings would be expected with immune thrombocytopenic purpora?
- decreased platelet count (thrombocytopenia)
- normal PT/PTT (not involved, primary hemostatis)
- increased megakaryocytes in bone marrow (increased platelet demand)
What are the different types of immune thrombocytopenic purpora?
- acute
- chronic
What is acute immune thrombocytopenic purpora?
What is its typical presentation?
-children
-weeks after a viral infection/immunization
**self-limiting, resolves within weeks**
What is chronic immune thrombocytopenic purpora?
What is its typical presentation?
- women of childbearing age
- idopathic (primary) or associated with other autoimmune disease (secondary)
- commonly associated with SLE
- also associated with HIV and B cell neoplasms (CLL)
What special consideration should be taken in women with chronic immune thrombocytopenic purpora?
IgG can cross the placenta, women with chronic ITP can have children that will display self-limited thrombocytopenia following birth
What is the treatment for immune thrombocytopenic purpora?
- corticosteroids (very effective in children; effective in adults but will likely relapse)
- splenectomy (eliminates both source of IgG and location of destruction)
- IVIG
- rituximab
What is drug-induced thrombocytopenia?
platelet destruction either by the direct action of a drug (primary) or immune mediated destruction caused by the drug (secondary)
What are common drugs associated with drug-induced thrombocytopenia?
- heparin
- quinine
- quinidine
- vancomycin
What is HIT?
Heparin-induced thrombocytopenia
destruction of platelets following heparin treatment (~5% of the population)
Type 1:
-immediate effect, little clinical significance
Type 2:
- delayed respone (1-2 weeks)
- causes platelets to aggregate resulting in paradoxical thromosis with thrombocytopenia
-can lead to loss of limbs or fatal PE
What is the mechanism of HIT?
- heparin binds platelet factor 4 (PF4) on platelets
- heparin-PF4 complex is recognized by certain antibodies
- some Ab coated platelets are removed by spleen -> thrombocytopenia
- some Ab coated platelets fragment and activate other platelets -> thrombosis
What is HIV-associated thrombocytopenia?
What are the mechanisms?
One of the most common symptoms of HIV infection
- platelet destruction and decreased production caused by HIV infection
- platelets/megakaryocytes have CD4 (target receptor of HIV) and can become infected -> decreased produciton and increased destruction
- HIV can also cause B-cell dysplasia with increased risk of autoimmune antibodies
How does microangiopathic hemolytic anemia relate to hemostasis?
the mircrothrombi formed use up platelets -> thrombocytopenia
What lab findings would be expected with microangiopathic hemolytic anemia?
- decreased platelets (thrombocytopenia)
- increased bleeding time
- normal PT/PTT (not involved, primary hemostasis)
- anemia w/ schistocytes
- increased megakaryocytes in bone marrow (increased demand for platelets)
What are the main types of microagniopathic hemolytic anemia?
- thrombotic thrombocytopenic purpora (TTP)
- hemolytic uremic syndrome (HUS)
What is TTP?
Thrombotic thrombocytopenic purpora
(a microangiopathic hemolytic anemia)
decrease in ADAMTS13 resulting in formation of thrombi resulting in thrombocytopenia
What is the mechanism of TTP?
caused by decreased ADAMTS13, most commonly autoimmune; can be genetic
ADAMTS13 cleaves multimeric vWF into monomers
decreased ADAMTS13 -> increased multimers -> abnormal aggregation -> microthrombi
What is the classic presentation of TTP?
- adult
- female
- petechiae/purpora
- microangiopathic hemolytic anemia
- fever
- CNS abnormalities (thrombi in brain)
What is the treatment for TTP?
- plasmaphoresis to remove offening Ab
- corticosteriods
What is HUS?
Hemolytic uremic syndrome
(a microangiopathic hemolytic anemia)
infection (most commonly dysentery from E coli O157:H7) induced endothelial damage resulting in platelet activation
typically results in renal damage (hence uremic)
