Disorders Of Platelets Question And Answers

Disorders Of Platelets Important Notes

1. Partial thromboplastin time

  • Used to measure the intrinsic factors as well as factors common to both intrinsic and extrinsic pathways
  • The normal range is – 30-40 sec
  • Causes of prolonged partial thromboplastin time are
  • Parenteral administration of heparin
    • DIC
    • Liver disease
    • Circulating anticoagulants

2. Thrombin time

  • It is semi-quantitative test for fibrinogen deficiency
  • Normal range – 20-30 sec
  • Common causes of prolonged thrombin time are
    • Presence of heparin
    • DIC

3. Bleeding time

  • Normal range – 3-8 min
  • Prolonged in
    • Thrombocytopenia
    • Von Willebrand disease
    • Vascular abnormalities
    • Disorders of platelet functions

4. Clotting time

  • Normal range – 4-9 min
  • Prolonged in
    • Hemophilia
    • Vitamin K deficiency
    • Liver diseases
    • Anticoagulant administration

5. Von Willebrand disease

  • It occurs due to qualitative defect in Von Willebrand factor in blood
  • It is characterized by
    • Normal platelet count
    • Prolonged bleeding time
    • Defective platelet aggregation
    • Reduced factor 8 activity

6. DIC (Disseminated Intravascular Coagulation)

  • It is characterized by systemic activation of the blood coagulation system
  • Results in the generation and deposition of fibrin leading to Microvascular thrombi in various organs
  • Severe bleeding complications occur
  • It is seen in promyelocytic leukaemia

Disorders Of Platelets Long Essays

Question 1. What is disseminated intravascular coagulation? Describe its etiopathogenesis.
Answer:

Disseminated Intravascular Coagulation: Disseminated intravascular coagulation is a complex thrombo-hemorrhagic disorder occurring as a secondary complication in some systemic diseases

Disseminated Intravascular Coagulation Etiopathogenesis: Pathogenesis of DIC includes the following events

1. Activation of coagulation: Etiological factors like massive tissue injury, presence of infections, and endothelial damage causes activation of coagulation by the release of tissue factor

2. Thrombotic phase:

  • Endothelial damage from various thrombogenic stimuli causes:
    • Generalized platelet aggregation
    • Platelet adhesion
    • Deposition of small thrombi and emboli throughout microvasculature

3. Consumption phase: Consumption of coagulation factors and platelets occurs

4. Secondary fibrinolysis:

  • The fibrinolytic system is secondary activated
  • This causes the breakdown of fibrin resulting in formation of FDPs in circulation

Disorders Of Platelets Intravascular Coagulation

Disorders Of Platelets Short Essays

Question 1. Bleeding time
Answer:

  • Bleeding time (BT] is defined as the time lapse between skin puncture and the arrest of bleeding.
  • BT is the time from the onset of bleeding to the stoppage for bleeding. The bleeding stops due to the formation of a temporary haemostatic plug.
  • Procedure: Under aseptic conditions, give a deep finger prick and note the time. Then remove the blood drop every 15 s by a clotting paper (along the edges] at a different spot till the bleeding stops. Count the number of spots and calculate BT as follows:
  • BT = Initial time + (number of spots – 1] x 15 s

Read And Learn More: Pathology Question And Answers

Bleeding Time Indications:

  • It is a useful screening test in patients with a history of prolonged bleeding.
  • In patients with bleeding disorders before any surgical procedures.

Bleeding Time Interpretation: An abnormal BT is usually the result of

  • Abnormalities in the structure or ability of capillary blood vessels to contract or
  • Abnormalities in the number or functional integrity of the platelets.

Question 2. Thrombocytopenia
Answer: Thrombocytopenia is defined as a reduction in the peripheral blood platelet count below the lower limit of normal i. e., below 1,50,000/microlitre

  • Platelet counts in the range of 20,000 – 50,000 cells/microlitre are associated with an increased risk of post-traumatic bleeding.
  • Spontaneous bleeding is evident when the count falls below 20,000 cells/microlitre

Thrombocytopenia Causes:

1. Impaired platelet production:

  • Generalised bone marrow failure.
  • Aplastic anaemia, leukaemia, megaloblastic anaemia, marrow infiltration.
  • Selective suppression of platelet production.
    • Drugs (Anticancer, cytotoxic, alcohol], Infection (HIV, measles].

2. Accelerated platelet destruction:

  • Immunologic destruction.
    • Autoimmune – ITP, SLE
    • Drug associated – Heparin, sulfa compounds.
    • Infections – HIV, cytomegalovirus infections.
  • Non – immunologic destruction,
    • DIC
    • Gaint haemangiomas
    • TTP

3. Splenic Sequestration: Splenomegaly.

4. Dilutional loss: Massive transfusion of old stored blood to bleeding patients.

Thrombocytopenia Clinical features:

  • Usual manifestations are petechial haemorrhage, purpura, easy bruising, epistaxis, mucosal bleeding such as menorrhagia in women, nasal bleeding, bleeding from gums, and haematuria.
  • Intracranial haemorrhage is rare.
  • Splenomegaly, hepatomegaly may also occur.

Thrombocytopenia Investigations:

  • Low platelet counts,
  • Prolonged bleeding times,
  • Normal coagulation profile
  • Abnormal long clot retraction time.

Thrombocytopenia Treatment:

  • Platelet transfusion.
  • Treatment of the underlying cause.

Question 3. Hemophilia
Answer:

  • Haemophilia is a X-linked recessive disorder characterised by the deficiency of factor 8 (Haemophilia A] classic haemophilia]
  • Whereas inherited deficiency of factor 9 (Christmas factor/plasma thromboplastin component] produces Christmas disease/haemophilia B. (Christmas disease].

Hemophilia A: Pathogenesis: It is caused by quantitative reduction of factor 8 in 90% of cases while 10% have normal/increased level of factor 8 but reduced activity.

Hemophilia A Clinical features:

  • In severe cases -Bleeding is spontaneous.
  • In mild disease – Bleeding is rarely spontaneous
  • Bleeding occurs mainly in joints (Haemarthrosis), muscles (haematoma), and viscera/in retroperitoneum but in can involve any organ system.
  • Spontaneous intracranial haemorrhage and oro-pharyngeal bleeding are rare, but when they occur they are the most feared complications.

Hemophilia A Treatment: Factor 8 replacement therapy, consisting of factor 8 concentrates/plasma cryoprecipitates.

Haemophilia B:

  • Haemophilia B is rarer than haemophilia A.
  • Inheritance patterns and clinical features of factor 9 are indistinguishable from those of classic haemophilia but accurate laboratory diagnosis is critical since haemophilia B requires treatment with different plasma fractions.

Hemophilia B: Treatment: infusion of either fresh frozen plasma/plasma enriched with factor 9

Question 4. Von Willebrand’s disease
Answer:

Von Willebrand’s Disease: Is the most common hereditary coagulation disorder occurring due to qualitative/quantitative defects in Von Willebrand’s factor.

  • Von Willebrand factor is a multimeric plasma glycoprotein synthesized by megakaryocytes and endothelial cells. It serves two major functions asfollows.
  • Acts as a carrier protein for factor 8.
  • Helps in the adhesion of platelets to subendothelial collagen.

Von Willebrand’s Disease Clinical features:

  • Spontaneous bleeding from mucous membranes and excessive bleeding from wounds.
  • Gastrointestinal bleeding.
  • Epistaxis, menorrhagia, and superficial bruises are present

Von Willebrand’s Disease Lab investigations:

  • Prolonged bleeding time,
  • Normal platelets count,
  • Bleeding time increased,
  • Reduced vWF levels, factor 8 activity reduced.

Von Willebrand’s Disease Treatment:

  • Factor 8 and vWF concentrate transfusion,
  • The bleeding episodes can be managed by giving vasopressin which increases the vWF levels.
  • Persistent bleeding is treated with factor 8 concentrate.
  • Cryoprecipitate transfusion
  • Antifibrinolytic agent
  • Example: Tanexamie acid is useful in conjunctive therapy during dental procedures.

Question 5. Pancytopenia
Answer: Pancytopenia means the occurrence of anaemia, leukopenia and thrombocytopenia together.

The causes of pancytopenia are as follows:

1. Aplastic anaemia

2. Pancytopenia with normal or increased marrow cellularity.

  • Myelodysplastic syndromes
  • Hypersplenism
  • megaloblastic anaemia

3. Paroxysmal nocturnal haemoglobinuria

4. Bone marrow infiltrations.

  • Haematologic malignancies (leukaemias, lympho-mas, meylomas)
  • Nonhaematologic metastatic malignancies
  • Storage diseases
  • Osteopetrosis.

Question 6. Idiopathic Thrombocytopenic Purpura.
Answer: It is characterized by the immunologic destruction of platelet and normal or increased megakaryocytes in bone marrow

Idiopathic Thrombocytopenic Purpura Types:

  1. Acute
  2. Chronic

Idiopathic Thrombocytopenic Purpura Clinical Features:

  • Usual manifestations
  • Petechial haemorrhage
  • Purpura
  • Easy bruising
    • Epistaxis
    • Mucosal bleeding such as menorrhagia in women
    • Nasal bleeding
    • Bleeding from gums
    • Hematuria
  • Intracranial haemorrhage is rare
  • Splenomegaly, hepatomegaly may also occur

Idiopathic Thrombocytopenic Purpura Lab Diagnosis:

  • Diagnosis can be made from the following findings
    • Thrombocytopenia
    • Microangiopathic haemolytic anaemia
    • Leucocytosis
    • Bone marrow aspiration shows increased megakaryocytes
    • Examination of biopsy shows typical microthrombi in arterioles, capillaries and venules

Disorders Of Platelets Short Question And Answers

Question 1. Prothrombin time
Answer:

  • Prothrombin measures the extrinsic system factor 7 s well as factors in the common pathway
  • In it, tissue thromboplastin and calcium are added to the test

Normal Time: 10-14 seconds

Prolonged In:

  • Administration of oral Anticoagulants
  • Liver disease
  • Vitamin K deficiency
  • Disseminated intravascular coagulation

Question 2. Screening tests for bleeding disorders
Answer:

Disorders Of Platelets Screening tests for bleeding disorders

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