Hemorrhagic, Thrombotic, and PLT disorders

Common causes of acquired factor deficiencies

Liver disease, Vitamin K deficiency, Auto immune disorders

How does Liver disease cause a factor deficiency

Suppresses production of clotting factors + vitamin K dependent factors

• May lead to dysfibrinogenemia and poorly functioning fibrinogen

How does vitamin K deficiency cause factor deficiencies

Vitamin K is required for Vit.K dependent clotting factors. Factors are produced in their de-carboxylated forms which cannot participate in coagulation

Autoimmune factor deficiencies

Antibodies produced that inhibit II, V, VIII, IX, XIII, vWF (VIII most common)

Acquired hemophilia also associated with rheumatoid arthritis, IBD, SLE, lymphoproliferative diseases, pregnancy

Lab results with autoimmune factor defieciencies

Prolonged coag studies not corrected in mixing studies in the presence of an inhibitor.

Inhibitor screens will be positive, and single factor assays show increase factor activity with increasing dilutions

What is Von WIllebrand Disease

Hereditary deficiency of vWF (auto-dominant inheritance). Can be qualitative or quantitative defects

Common symptoms of Von Willebrand disease

Mucocutaneous bleeding (due to inability of PLTs to adhere)

Also low FVII since vWF stabilizes VIII

Treatment of Von Willebrand Disease

Desmopressin - triggers release of vWF from endothelial cells

Humate-P (vWF and FVIII mixture)

Coag study results of Von WIllebrand Disease (PT, PTT, PLT count, Bleeding time, factor assays, PLT aggregation)

PT - Normal

PTT - normal to prolonged

PLT count normal

Bleeding time prolonged

vwF antigen assay: low

FVIII assay: low

PLT aggregation: Ristocetin variable depending on type of disease

Ristocetin co-factor assay; no aggregation

What is Hemophilia A

Congenital FVIII factor deficiency (X-linked recessive). Factor levels indicate severity of the disease

Symptoms of Hemophilia A and B (severe)

Intracranial + Intramuscular bleeding, Hematuria, spontaneous hemorrhage requiring daily factor replacement

Coag study results for Hemophilia A

PT: normal

PTT: prolonged

Thrombin Time: normal

Inhibitor screen: normal

Bleeding time: normal

What is Hemophilia B

Hereditary Factor IX deficiency (X-linked recessive). Similar symptoms to Hemophilia A

Coag study results of Hemophilia B

PT: normal

PTT: prolonged

Bleeding time: normal

What is Hemophilia C

Inherited (auto dominant) factor XI deficiency. Has mild to severe symptoms depending on deficiency or factor activity

Coag study testing results of Hemophilia C

PT: normal

TT: normal

PTT: prolonged

Inhibitor screen: normal

Bleeding time: normal

What is hypofibrinogenemia

Inherited (auto recessive) or acquired disorder leading to low levels of fibrinogen in plasma. Levels usually 0.2-1.0 g/L with mild bleeding episodes

Coag testing results of Hypogibrinogenemia

PT: prolonged

PTT: prolonged

Thrombin time: prolonged

FIbrinogen: abnormal

Bleeding time: prolonged

What is afibrinogenemia

Autosomal recessive disorder causing absence of functionally detectable fibrinogen in plasma (levels usually <0.5 g/L)

Afibrinogenemia symptoms

Profuse bleeding after slight trauma and delayed wound healing. Primary hemostasis is also affected with abnormal PLT adhesion and aggregation

Coag testing results for afibriogenemia

PT: Abnormal

PTT: Abnormal

TT: abnormal

Fibrinogen: abnormal

Bleeding time: prolonged

PLT studies: abnormal

What is Dysfibrinogenemia

Autosomal dominant disorder causing alteration in the structure of the fibrinogen molecule. Changes in the structure of fibrinogen affect normla interaction of fibrinogen with enzymes and cofactors = bleeding

Can also be acquired due to liver disease, cancer, fibrinolysis, DIC

Symptoms of dysfibrinogenemia

Bleeding due to impaired fibrinolysis, thrombophilia may result due to lack of fibrinogen binding to thrombin

Coag testing results of dysfirbinogenemia

PT normal

PTT normal

BT variable

TT prolonged

PLT function normal

Reptilase time very prolonged

What are Contact Factor Deficiencies

hereditary Deficiencies in FXII, HMWK, and Prekallikrein (autosomal recessive). Often asymptomatic and not associated with bleeding, but there may be increased risk of thrombosis due to inadequate activation of fibrinolysis

Coag testing results of contact factor deficiencies

PT normal

PTT abnormal

TT normal

BT normal

Factor assay: decreased or low

What is Factor XIII deficiency

Deficiencies leading to decreased cross linking of fibrin monomers resulting in weak clots, defective wound healing, slowly resolving hematomas, and hemorrhage

What is APC resistance (FV Leiden)

Autosomal dominant inheritance disorder causing a FC defect so that it cannot be bound by activate protein C. FV remains active in the cascade and activates/produces more thrombin. Patients at risk of thrombosis

How to test for Factor V Leiden

Genetic testing or:

Activate protein C resistance ratio:

• Patient plasma mixed with 1:4 factor V depleted plasma and PTT reagent

• Two aliquots tested: one mixed with CaCl2 and one with CaCl2 + APC

• Reaction ni mixture with APX should be prolonged to a clotting time at least 1.8X longer than without APC

• Less than 1.8 = FVL

What is Prothrombin G20210A mutation

Mutation in prothrombin gene causes carriers to have elevated plasma prothrombin + activity = risk of thrombosis

How to test for Prothrombin G20210A mutation

Genetic testing

What are hereditary Protein C or S deficiencies

Activated Protein C (activated by thrombin:thrombomodulin complex) binds to protein S on endothelial cell or PLT Pls. The complex inactivates factor V and VIII. Deficiencies can cause DVT and PE. Protein S def may lead to strokes

How to test for protein C or protein S deficiency

Clot based assays and antigenic assays to measure protein C and S levels

What is Lupus Anticoagulant/antiphospholipid antibody syndrome (LAC)?

LAC is a nonspecific inhibitor binding to protein-phospholipid complexes in vitro. It also binds to prothrombin, interfering with activation (II to IIa)

Do LACs cause risk for hemorrhage?

No. Patients do not bleed in vivo, but are prone to thrombosis (strokes, coronary artery disease, DVT, pulmonary emboli)

The Ab only reacts to in vitro phospholipids. so only in vitro testing causes prolonged clotting

What can cause the formation of LAC’s?

Arise in response to infections, or drugs, and dissappear within 12 weeks

Also can arise secondary to collagen vascular diseases such as SLE, RA.

Coag testing results of LAC

PT: normal or prolonged

PTT: prolonged

TT: normal

Mixing study: no correction

Dilute Russel Viper Venom Time: Shortened

Use of dilute rissel viper venom

Venom initiates the coag cascade by activating factor X. Poor in reagent PL and is sensitive to the presence of LAC

Causes of decreased or defective PLT production

Megakaryocyte hyperplasia, Infiltrative processes (myelofibrosis, leukemia, lymphoma, cancer), Ineffective production of Megakaryocytes (megaloblastic anemia, MDS)

What can cause Megakaryocyte hypoplasia

Genetic forms (auto rec, auto dom, X-linked)

Neonatal hypoplasia caused by infection or in-utero drug exposure

Acquired: Radiation, chemo, viral infections, drugs

Causes of Increased removal of PLTs due to antibodies

Immune thrombocytopenic purpura (ITP)

Neonatal allo/autoimmune thrombocytopenia

Drug induced thrombocytopenia

Heparin Induced THrombocytopenia

What is immunoe thrombocytpenic purpura

IgG antibodies against GPIa or IIb/IIIa attach to platelets, and these DAT pos platelets are removed in the spleen. Reduces lifespan of platelets to a few hours

PBS appearance of ITP

Abnormally large platelets, and platelet fragments (analogous to schistos). WBCs are RBCs are normal in the basenc eof bleeding

Treatment for ITP

Corticosteroids (reduce auto-Ab produciton) IV gama globulin (saturate macrophage), platelet transfusion, splenectomy, immunosuppresive drugs

What is Neonatal alloimmune thrombocytopenia

Mother may develop antibodies against platelet specific antigens on fetal platelets which she lacks, and which are inherited from the body. Same mechanism as HDFN

Drug induced thrombocytopenia - anti-drug Ab mechanism

Drug induces formation of anti-drug antibody which interacts with platelets only in the presence of the drug. The platelets are removed by the spleen

Drug induced thrombocytopenia - Hapten mechanism

Drug acts as a hapten andcombines with a plasma protein to form a complex that acts as an antigen. Patient produces Abs against the complex. The Ab binds to the PLT membrane and causes removal in the spleen

Drug induced thrombocytopenia - drug independent mechanism

The drug stimulates the formation of an autoantibody. The antibodies bind to glycoprotein receptors with no requirement for the presence of the free drug. Mechanism is not super clear how it happens

Drug induced thrombocytopenia - Heparin induced thrombocytopenia (HIT) mechanism

Heparin binds to platelet factor 4 on the plate. This causes a conformational change in PF4 which results in exposure to new epitopes, and stimulates the immune system to make an antibody to PF4/heparin complex. Antibody binds with Fab portion, then Fc portion binds to the platelet Fc receptor causing platelet activation and aggregation with thrombosis

How does the HIT assay work

1) anti-heparin antibodies are detected in the serum by challenging washed normal platelets with test sera in the presence of high concentrations and low concentrations of heparin.

2) only therapeutic levels of heparin will induce platelet activation

3) get ATP release and platelet aggregation if the HIT antibody is present in the test sera. (measured by plt aggregometry)

What is Bernard Soulier Syndrome

Autosomal recessive disorder causing the GPIb complex to be missing from the platelet surface, or the complex exhibits abnormal function. The platelets cannot bind to vWF, so they have defective adhesion

Common symptoms of Bernard Soulier syndrome

Nosebleeds, Ecchymosis, gingivial hemorrhage, GI bleeds

Typical smear features of Bernard Soulier syndrome

See giant platelets on the PBS, BM shows normal or increased amounts of Megakaryocytes

Coag study results of Bernard Soulier syndrome

PT and PTT - normal

PLT count - mild thrombocytopenia (40 - normal)

Bleeding time - prolonged

PLT aggregation studies: normal aggregation with ADP, epinephrine, collagen, arachidonic acid. No response to ristocetin, diminished response to thrombin

What is Glanzmann’s Thrombasthenia

Autosomal recessive disorder causing a defect on PLT GPIIb/IIIa receptor. Due to the defect, platelets cannot adsorb fibrinogen, vWF, fibronectin, and aggregation is defective

Symptoms of Glanzmann’s Thrombasthenia

Severe hemorrhage incl. epitaxis, hematomas, menorrhagia, GI bleeds

Coag study results of Glanzzmann’s Thrombasthenia

PT and PTT normal

PLT count and morphology normal

Prolonged bleeding time

PLT aggregation studies: Normal aggregation with ristocetin, but lack of aggregation with ADP, collagen, thrombin, and epinephrine

What is dense granual deficiency

Platelets are missing dense granules, causing coagulation issues often due to a lack ADP secretion from the platelets

2 types of dense granule deficiencies

Non-albinism: dense granules are present but there’s an inability to package granule contents

Albinism: Profound dense granule deficiency

Platelet aggregation study results for dense granule deficiency

No response to arachidonic acid, epinephrine and ADP induce a primary wave of aggregation only

What is alpha granule deficiency

Autosomal recessive disorder causing an absence of alpha granules in platelets, leading to an irregular appearance of platelets on the PBS. Patients have lifelong bleeding tendencies

Lab tests of alpha granule deficiency

PT and PTT normal

PLT count - decreased, platelets are large in size and agranular

Bleeding time- prolonged