Flashcards in Ch4 - 1) Primary Hemostasis and Bleeding Related Disorders Deck (67)
normal 150-400 K/pL; < 50 K/pL leads to symptoms,
normal 2-7 minutes; prolonged with quantitative and qualitative platelet disorders
used to assess number and size of platelets
Bone marrow biopsy
used to assess megakaryocytes, which produce platelets
What is immune thrombocytopenic purpura?
(ITP) is an autoimmune production of IgG against platelet antigens (GPIIb/IIIa)
What is the most common cause of thrombocytopenia in children and adults?
immune thrombocytopenic purpura
In ITP what results in thrombocytopenia?
Antibody-bound platelets are consumed by splenic macrophages
ITP is divided into?
acute and chronic forms
Acute form of ITP?
arises in children weeks after a viral infection or immunization;selflimited, usually resolving within weeks of presentation
Chronic form of ITP?
arises in adults, usually women of chilbearing age. May be primary or secondary (e.g SLE).
What is the risk involved in chronic ITP?
May cause short-lived thrombocytopenia in offspring since antiplatelet IgG can cross the placenta.
laboratory findings for ITP include
decreased platelet count, often < 50 K/pL, Normal PT/FTT, Coagulation factors are not affected. increased megakaryocytes on bone marrow biopsy
What is the Initial treatment for ITP?
How will children and adults respond to the initial treatment for ITP?
Children respond well; adults may show early response, but often relapse.
In addition to corticosteroids what else is used in the treatment of ITP?
IVIG is used to raise the platelet count in symptomatic bleeding, but its effect is short-lived,
What is a permenant solution for patients with ITP?
Splenectomy eliminates the primary source of antibody and the site of platelet destruction (performed in refractory cases).
What is microangiopathic hemolytic anemia?
Pathologic formation of plateletmicrothrombin small vessels
How are plateletmicrothrombin formed and what is the result?
Platelets are consumed in the formation of microthrombi sheering the RBCs as they cross microthrombi, resulting in hemolytic anemiawith schistocytes
What is microangiopathic hemolytic anemia seen in?
thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS)
What is TTP due to?
decreased ADAMTS13 which is an enzyme that normally cleaves vWF multimers into smaller monomers for eventual degradation.
How does TTP lead to microangiopathic hemolytic anemia?
1. Large, uncleaved multimers lead to abnormal platelet adhesion, resulting in microthrombi.
Decreased ADAMTS13 is usually due what?
an acquired autoantibody;
TTP is most commonly seen in?
HUS is due to?
Hemolytic uremic syndrome is due to endothelial damage by drugs or infection.
HUS is classically seen in?
children with E coli G157;H7 dysentery, which results from exposure to undercooked beef
How is E Coli related to microangiopathic hemolytic anemia?
E coli verotoxin damages endothelial cells resulting in platelet microthrombi
The clinical findings for HUS and TTP include
Skin and mucosal bleeding, Microangiopathic hemolytic anemia, Fever, Renal insufficiency, CNS abnormalities
Renal insufficiency is more common in HUS or TTP?
HUS ? thrombi involve vessels of the kidney
CNS abnormalities are more common in HUS or TTP?
TTP ? Thrombi involve vessels of the CNS