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 a 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 cause 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 the formation of FDPs in circulation

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 of 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 with 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 and 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 an 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 levels 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 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: This 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 as follows.
• 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, myelomas)
• Nonhaematologic metastatic malignancies
• Storage diseases
• Osteopetrosis.

Question 6. Idiopathic Thrombocytopenic Purpura.
Answer: It is characterized by the immunologic destruction of platelets 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 and 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 as 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: