Exam Final Flashcards
Three main mechanisms for bleeding disorders
- blood vessel fragility/damage
- platelet deficiency or dysfunction
- Derangement of coagulation pathway
Vessel wall abnormality bleeding
- common but serious cause of bleeding
- small hemorrhages- petechiae and purpura of skin and mucous membranes
- PT, PTT, and platelets normal
Infection source of Vessel wall abnormality bleeding
meningococcus and other septicemia, microbial damage to microvasculature or DIC - petechiae/purpura
Drug reaction sources of Vessel wall abnormality bleeding
Drug induced immune complex in vessel wall and hypersensitivity vasculitis (leukocytoclastic) - palpable purpura
Scurvy and Ehlers-Danlos source of Vessel wall abnormality bleeding
Collagen defects weaken vessel wall- easier breaking of vessels
Henoch-Schonlein purpura source of Vessel wall abnormality bleeding
- systemic immune disorder, deposited immune complexes in vessels throughout the body - rash, abdominal pain, arthralgia, acute glomerulonephritis
Perivascular amyloid source of Vessel wall abnormality bleeding
Causes muco-cutaneous petechiae
What is considered thrombocytopenia?
Platelet count less that 100,000/uL
What platelet level can aggravate posttraumatic bleeding?
- 20,000-50,000/uL
What platelet level is associated with spontaneous bleeding?
<20,000/uL
thrombocytopenia bleeding usually involves
Small vessels: skin, mucous membranes of GI/GU tract, intracranial bleeds are the most severe complications
Four categories of thrombocytopenia
- Decreased platelet production (aplastic anemia, leukemia, drug, HIV, EtOH)
- decreased platelet survival/increased consumption (immune ITP, non-immune DIC or thrombo. microangiopathy)
- Platelet sequestration (spleen 30-35% of bodies platelets, 80-90% with splenomegaly)
- Dilution (massive transfusion, viable platelets decrease with time in stored blood)
Chronic Immune Thrombocytopenic Purpura (ITP)
- autoantibody mediated platelet destruction (usually to GP2b3a or 1b9, majority IgG
- Secondary: predisposing condition (SLE, HIV, CLL)
- Primary: idiopathic ( exclusion of secondary)
- splenectomy improves thrombocytopenia due to decreased phagocytosis and sequestration and decreased autoantibodies by decreasing plasma cells
What is seen morphologically in ITP?
- normal size spleen, sinusoidal congestion and enlarged lymph follicles
- BM: modestly increased numbers of megakaryocytes, immature/not specific indicating increased thrombopoiesis
- PBS: abnormally large platelets (megathrombocytes)
What are the clinical presentations of ITP?
- Female, under 40
-insidious bleeding onset, skin and mucosal surfaces - Hx of nosebleeds, easy bruising, gum bleeding, bruising from minor trauma
- Subarachnoid hemorrhage
- splenomegaly/lymphadenopathy RARE, suggests secondary to B cell neoplasm
Treatment for ITP
- Glucocorticoids first line, may relapse a year or more later
- IVIg or anti-CD20 used in relapse
- Splenectomy
Acute immune thrombocytopenic purpura
- Autoantibodies to platelets
- disease of CHILDHOOD
-abrupt onset 1-2 weeks post self-limited viral illness trigger - usually resolves after 6 months
- glucocorticoids only if thrombocytopenia is severe
- 205 develop chronic ITP
Drug induced thrombocytopenia
- Direct effect or immune mediated
- quinine, quinidine, vancomycin bind platelet glycoproteins creating antigenic determinants recognized by antibodies
- platelet inhibitory drugs bind GP2b3a and create and immunogenic epitope
- heparin induced thrombocytopenia
HIV associated thrombocytopenia
- one of the most common hematologic issues in HIV infection
- impaired production and increased destruction
- CD4 and CXCR4, HIV receptor and co receptor found on megakaryocytes
Thrombotic thrombocytopenic purpura (TTP)
- pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, transient neurological defects, and renal failure
- associated with deficiency in plasma emzyme ADAMTS13, von willebrand factor metalloprotease which degrades VHMW multimers of vWF
- high platelet consumption –> low count
Hemolytic Uremia Syndrome (HUS)
- absence of neurologic symptoms, prominence of renal failure, and occurrence in children
- Strong association with infectious gastroenteritis (e.coli O157:H7)
- Toxin alters endothelial function resulting in platelet activation and aggregation
- Bloody diarrhea is the first symptom
Inherited disorders of platelet dysfunction
- Defects of platelet adhesion
- Defects of platelet aggregation
- Disorders of platelet secretion
Bernard-Soulier syndrome
- inherited defect of platelet function
- autosomal recessive
- defect of platelet adhesion to sub-endothelial matrix, defect of GP complex 1b-9, poor binding to VWF
- abnormally large platelets
- variable, severe bleeding
Glanzmann thrombasthenia
- inherited defect of platelet function
- autosomal recessive
- platelets fail to aggregate in response to ADP, collagen, epinephrine, or thrombin
- deficiency of GP 2b3a
- often severe bleeding tendency
Aspirin and non-steroidal leading to acquired defects of platelet function
- COX inhibitors –> no TXA2 or PGI2 (needed for platelet aggregation and granule release
Uremia leading to acquired defect of platelet function
- Decreased GP1b complexes, poor adhesion
- reduced platelet function involving adhesion, granule secretion, and aggregation
- reduced fibrinogen binding, poor aggregation
Hemophilia A
- most common hereditary disorder associated with life threatening bleeding
- mutated factor 8 (essential for factor 9 in the clotting cascade)
- X-linked recessive affecting males and homozygous females
- severity of bleeding depends on level of factor 8 activity
Symptoms of hemophilia A
- Easy bruising and massive bleeding with trauma
- spontaneous hemarthrosis leading to debilitating joint deformities
- Prolonged PTT, normal PT (intrinsic pathway defect)
- Treat with infusion of recombinant factor 8
Hemophilia B
- Severe factor 9 deficiency
- X-linked recessive
- variable severity
- prolonged PTT, normal PT (intrinsic pathway defect)
- treat with infusion of recombinant factor 9
Von Willebrand Disease
- The most inherited bleeding disorder (1% of US adults)
- autosomal dominant
- mild bleeding tendency, unnoticed until procedure or other increased requirement for hemostasis
- presents with epistaxis/mucous membrane bleeding, menorrhagia, excess wound bleeding
Type 1 Von Willebrand Disease
- quantitative defect in vWF
- Autosomal dominant, mild-moderate severity
- spectrum of mutations resulting in poor maturation of the vWF proteins or its rapid clearance
- 70% of all cases, incomplete penetrance and variable expression
- Mild disease
Type 2 Von Willebrand disease
- Qualitative defects in vWF
- autosomal dominant, missense mutations inhibit multimer formation
- Severe subtypes
- 25% of all cases
- mild-moderate bleeding
Type 3 Von Willebrand disease
- quantitative defect in vWF
- Autosomal recessive, very low level of vWF
- severe deficiency
- marked effect on factor 8, bleeding resembles hemophilia
Von Willebrand counts
- normal platelet count, defect in platelet function
- active vWF decreased because vWF stabilizes factor 8, a secondary decrease of factor 8 occurs
- prolonged PTT in types 1 and 3
- can pretreat with factor 8 and vWF prior to surgery or dental work
Factor defects secondary to liver disease
- most clotting factors synthesized in the liver
- decreased production of anticoagulants also occurs
- patients risk for thrombotic and bleeding compliactions
- liver disease can cause prolonged PT and PTT
- all vitamin K dependent proteins decrease (2, 7, 9, 10)
Vitamin K deficiency
- leafy green veg or intestinal flora synthesis
- ## deficiency is seen in very ill patients subsisting on parenteral nutrition after 4-6 weeks, or alcoholics
What is DIC?
- acute, subacute or chronic thrombo-hemorrhagic disorder characterized by excess activation of coagulation and the formation of thrombi in the microvasculature
- consumption of clotting factors, fibrin, and platelets
- secondary activation of fibrinolysis
- can present with tissue hypoxia due to micro-thrombi in microvasculature, hemorrhage due to deficiency of factors and activation of fibrinolysis
What are the two main mechanisms that trigger DIC?
1.) release of tissue factor or other pro-coagulant (OB complications, burn injuries, adenocarcinoma mucin activating factor 10)
2.) Widespread injury to endothelial cells
What is DIC most likely associated with?
- OB complications (placental/fetal procoagulants or amniotic fluids entering circulation
- Malignant neoplasms (adenocarcinoma, APML-AML M3)
- Sepsis (bacterial endotoxin activating factor 7 or decreasing thrombomodulin)
- major trauma/burns/extensive surgery (release of tissue factor/factor 3)
Waterhouse-Friderichsen syndrome -DIC
- meningococci from blood, spinal fluid, or throat
- circulatory collapse- hypotension
- extensive purpura shock, prostration, cyanosis
- hemorrhagic destruction of adrenal gland
- characteristic up and down fever
Osler Weber Rendu syndrome
- autosomal dominant
- red spider-like lesions on oral and nasal mucosa
- dilated capillaries cause bleeding
- dilated vessels present in skin, lips, tongue, and GI
- Iron deficiency anemia
Senile purpura
- normal finding in elderly
- results from impaired collagen production and capillary fragility
- non-palpable purpura in areas of trauma
What treatment is commonly given in platelet disorders?
- Fresh frozen plasma (has all the clotting factors) is used in all coagulation disorders
- Cryoprecipitate: mostly factors 8, 13, vWF, fibronectin, and fibrinogen
Fanconi’s anemia:
Bone marrow failure, thrombocytopenia and macrocytes