Module 4: Disorders of Hemostasis (from module) Flashcards

Question

Increased destruction or utilization of platelets (3 causes)

Answer 1

Excessive consumption of platelets (TTP, DIC, HUS) Platelet antibodies Transfusions

Answer 2

condition where there is excessive PLT adhesion, aggregation and coagulation - Thrombotic Thrombocytopenic Purpura (TTP) - Disseminated Intravascular Coagulation (DIC) - Hemolytic Uremic Syndrome (HUS)

Answer 3

rare, fatal Caused by deficiency of ADAMTS-13 (enzyme required to break up ultra large von willebrands factors (ULVWF) multimers into smaller, less adhesive multimers) Congenital or due to ADAMTS-13 autoantibodies Results in presence of ULVWF in plasma and widespread PLT aggregation Specific Lab findings: Increased megakaryocytic in bone marrow Increased megathrombocytes in PBS Increased PLT aggregation in PBS Decreased PLT survival

Answer 4

Patient produced platelet autoantibodies Immune THrombocytopenic Purpura (ITP) -PLT antibody (usually GPIIb/IIIa or GPIB) sensitizes the PLT and causes premature removal by macrophages in spleen Development usually occurs after viral infection or drugs (or for no apparent reason) - may be acute (children) or chronic (esp. women 15-50yo) * *Chronic ITP is second most common cause of thrombocytopenia Specific Lab findings: Increased megakaryocytic in bone marrow PLT antibody in serum Decreased PLT survival PLT count 10-50 x10^9/L

Answer 5

Dilution with PLT poor donor blood (very rare) donor PLT may be sensitized by PLT antibody formed in the patient after a prior transfusion PLT may also be lost in extravascular circulation (e.g. heart pump, renal dialyser)

Answer 6

increased Splenic pooling of PLT will reduce the count in the blood Occurs in conditions that cause splenomegaly

Answer 7

Increased PLT count (less common than thrombocytopenia) >400 x10^9/L -can happen spontaneously -Often secondary to order disorder or condition Give patient aspirin Lab findings: increased PLT counts with abnormal morphology Increased Megakaryocytic Increased red cell fallout in the clot retraction test Normal or prolonged bleeding time Thrombocythemia = >1000 x10^9/L

Answer 8

Indicated by skin/mucosal hemorrhage with prolonged bleeding time and normal PLT count

Answer 9

Disorders of platelet secretion/release reaction Thrombasthenia (Glanzmann disease) Bernard-Soulier Syndrome (BSS)

Answer 10

1) Storage Pool diseases (granule defects) Secondary aggregation disorder a)Dense granules (storage for ADP, ATP, Ca, serotonin) b)Alpha granules (storage for proteins) - deficiency leads to agranular appearance of PLT (termed Gray PLT Syndrome) -PF3 activity reduced leading to defects in PLT aggregation 2)Primary secretion defect (enzymatic pathway defect) No quantity or content abnormalities of PLT granules Defect due to deficiencies of enzymes and messengers that transmit signals from surface receptors to cause the release of granule contents. LAB FINDINGS: bleeding time prolonged Normal PLT count

Answer 11

failure of primary aggregation caused by reduced amounts of the membrane glycoprotein GPIIb/IIIa Aggregation fails because fibrinogen cannot be bound to PLT membrane Lab findings: bleeding time greatly prolonged Clot retraction is defective PLT adhesion to collegen is normal PLT aggregation ABNORMAL with ADP, epinephrine, thrombin and serotonin PLT aggregation NORMAL with ristocetin

Answer 12

AKA giant platelet syndrome Failure of PLT adhesion caused by reduced amounts of GPIb/IX Adhesion fails because vWF cannot be bound to the PLT membrane Disorder shows severe subcutaneous, mucosal and visceral bleeding (often fatal)

Answer 13

reagent that forces vwf and GPIb to aggregate platelets

Answer 14

bernard-soulier syndrome | von willebrand disease

Answer 15

more common than inherited defects Drugs can cause transient defects in adhesion/aggregation ASA (acetylsalicylic acid/aspirin); can last 4-7 days Caffeine, carbenicillin, anti-inflammatory drugs, vasodilators, antihistamines, dextran, alcohol, ampicillin, epinephrine, sulfinpyrazone, heparin