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Block 3 > W5 LECT3 > Flashcards

W5 LECT3 Flashcards

1
Q

Name 2 broad classes of platelet disoders

A
  • Quantitative disoders
  • Qualitative disoders
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2
Q

Name 2 types of Platelet quantitative disoder

A
  • ITP
  • TTP
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3
Q

Name 2 types of platelet qualitative disoders

A
  • Glanzmann Thrombosthenia (Aggregation)
  • Bernard-Soulier Syndrome (Adhesion)
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4
Q

T/F:
All platelet disoders, no matter quantitative or qualitative, are either acquired or inherited

A

TRUE

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5
Q

Increased platelet consumption through formation of thrombus lead to what qualitative platelet disoder?

A

Thrombotic thrombocytopenic pupura

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5
Q

Increased platelet consumption due to antibody mediated destruction to platelet lead to what qualitative platelet disoder?

A

Immune thrombocytopenic Pupura (ITP)

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5
Q

Discuss the pathogenesis of ITP

A

1951 – Antibodies directed against platelet glycoproteins
*Immune Thrombocytopenic Purpura excluded for the 1st time

  • Antiplatelet antibodies directed against platelet specific glycoproteins»opsonised platelets destroyed in the spleen&raquo_space;shortened platelet half-life
  • 1980’s – In addition to increased platelet clearance, also decreased platelet production
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5
Q

Name 3 causes of thrombocytopenia

A
  • Decreased platelet production
  • Increased platelet consumption
  • Platelet sequestration by the spleen
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6
Q

What are the clinical presentations of ITP?

A
  • Primary
    *Children (1 – 5 years of age)
    *Platelet count <30 x 109/L
    *Generally preceding viral infection
  • Secondary
    *Lymphoproliferative neoplasm
    *Infections: Viral (HIV, EBV, CMV, Hepatitis)
    *Autoimmune disorders
  • Acute (newly diagnosed): ITP duration <3 months
  • Persistent: ITP duration 3 – 12 months
  • Chronic: ITP duration >12 months
  • Mucocutaneous bleeding
    May 2024 NHLS-University of the Witwatersrand 8
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7
Q

Discuss the management of ITP

A
  1. First Line Therapy
    *Corticosteroids (CS)
    *IV Immunoglobulin (IVIG) – used with CS when a more rapid
    increase in platelet count is required
    *Either IVIG or Anti-D (in appropriate patients) if CS contra-
    indicated
  2. Second Line Therapy
    *Rituximab (anti-CD 20 monoclonal antibody)
    *Thrombopoietin Receptor Agonists (TPO-RA)
    *Splenectomy
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8
Q

How to carry out ITP investigations?

A
  1. FBC
    -Thrombocytopenia (platelet count <30 109/L)
    -Platelet morphology: typically normal, with varying numbers of large platelets
  2. Exclude secondary causes:
    * Liver function test
    * Thyroid function test
    * Haematinics: Vitamin B12 and folate
    * Infections
    * Viral screen: HIV, Hepatitis B/C, CMV, EBV
    * Bacterial: Cultures (if clinically appropriate)
    * Malaria screen
    * Mycobacterial (TB), etc
    * Coagulation screen: PT, aPTT, D-dimers
    * Autoimmune: ANA, Rheumatoid factor, ACLA, Lupus anticoagulant
    * Clinical examination and Imaging to assess spleen size
  3. Bone Marrow investigation: exclude other causes, normal / increased megakaryocytes
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9
Q

A qualitative platelet disoder that falls under the category of Thrombotic Microangiopathies (TMA)
* DIC, HUS, aHUS, HELLP

A

TTP

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10
Q

Haematological Emergency

A

TTP

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10
Q

Characterised by low platelets with micro-angiopathic
haemolytic anaemia

A

TTP

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10
Q

To see o the peripheral blood picture of Thrombotic Microangiopathies

A

schistocytes- RED CELL FRAGMENTS

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11
Q

Aetiology of TTP

A
  1. Inherited / Congenital:
    * Very rare
    * Severe deficiency of ADAMTS13 (metalloprotease with
    thrombospondin repeats)
  2. Acquired:
    * Idiopathic
    * HIV
    * Pregnancy
    * Transplant
    * Malignancy
    * Connective Tissue Disorders / Autoimmune
    * Drugs - Tacrolimus
    * Toxins
12
Q

Diagnoses of TTP

A

THE PENTAD:

A. LABORATORY:

  1. Thrombocytopenia
    -Platelet count <20-30 x 109/L
  2. Micro-angiopathic haemolytic anaemia (MAHA)
    -Schistocytes / red cell fragmentation on the peripheral blood smear (PBS)
    -Haemolytic screen: Elevated LDH, low haptoglobin, elevated reticulocyte production index (RPI), elevated unconjugated hyperbilirubinaemia,
    negative Coomb’s test
    -(Coagulation screen are typically normal)

B. CLINICAL:

  1. Neurological deficits/abnormalities
  2. Renal dysfunction/failure
  3. Fever

C. Confirmation of the ADAMTS13 deficiency
*Deficiency of the ADAMTS13 activity level
* ADAMTS13 antigen levels vary

12
Q

Management of TTP

A
  1. Supportive:
    *Avoid Platelet Transfusion
    *Aim for optimal haemoglobin (Hb)
    *Monitor for seizures, exclude acute coronary syndromes
    *Folic acid
    *Fluid resuscitation and maintenance
    *Find and Treat the cause (e.g. HIV = ART)
    *Consider Prednisone 1mg/kg/day (↓ circulating auto-antibodies)
    *Anticoagulation/antiplatelet when platelet count > 50 x 109/L
  2. Specific:
    *Therapeutic Plasma Exchange (TPE)
    *Solvent Detergent (S/D) Fresh Frozen Plasma (FFP) may be used in the interim
12
Q

Characteristics of inherited qualitative platelet disoders

A
  • Rare, described in few families
  • Mild: presents later in life, with haemostatic challenge
  • Severe: from early childhood or neonate
  • Specialist management: haemophilia centre or
    specialised bleeding disorder centre
13
Q

Name all the characteristics of Glanzmann thrombasthenia as one of the qualitative platelet disoders

A
  • Autosomal Recessive
  • Platelet aggregation disoder
  • Glycoprotein IIb/IIIa
  • Severe mucocutaneous bleeding
  • Normal platelet count with normal sized platelets
  • No aggregation on addition of ADP, collagen, Adrenaline, Arachidonic acid
  • Flow Cytometry: GPIIb(CD41)/IIIa(CD61) deficient
14
Q

Name all the characteristics of Bernard-Soulier Syndrome, as one of the qualitative platelet disoders

A
  • Autosomal Recessive
  • Platelet adhesion disoder
  • Glycoprotein Ib/IX/V
  • Mild-moderate mucocutaneous bleeding
  • Thrombocytopenia (to normal) with large platelets
  • Aggregation is absent with the addition of Ristocetin
  • Flow Cytometry: GPIb(CD42b) deficient
14
Q

List 3 qualitative acquired platelet disoders

A
  1. Systemic
    * Renal disease – Uremia → impaired vessel wall-platelet and platelet-platelet interaction
    * Liver disease – abnormal aggregation to ADP
  2. Haematologic
    * Myelodysplasia (MDS) – impaired platelet aggregation
    * Myeloproliferative neoplasm (MPN) – leucocyte-platelet interaction, storage pool
    deficiency, impaired platelet aggregation, decreased glycoprotein expression and
    fibrinogen binding after platelet activation
    * Paraproteinaemia (Myeloma) – adsorption of abn. proteins onto platelet membranes
  3. Drugs
    * Cyclo-oxygenase inhibitors: Salicylates (Aspirin), NSAIDs prevents platelet aggregation
    * Platelet Receptor Antagonists:
    *Glycoprotein IIb/IIIa inhibitors (abciximab)
    *Thienopyridines P2Y12 inhibitors (clopidogrel)
    * SSRIs (fluoxetine): diminished serotonin release on platelet activation → decreased
    platelet aggregation
    May 2024 NHLS-University of the Witwatersrand 22
14
Q

Name the 2 types of bleeding patterns

A
  1. Platelet type
    -From defect in primary hemostasis
    -Characterized by mucosal cutenous bleeding
    -Petechiae
  2. Clotting factor type
    -From defect in 2nday hemostasis
    -Characterized by bleeds into muscles, joints, internal organs
    -Ecchymoses
14
Q

Investigation of Platelet Disorders

A
  1. Screening Tests
    *Full Blood Count (FBC) and Peripheral Blood Smear (PBS)
    *Bleeding Time
    * Platelet Function Assay
  2. Diagnostic Tests
    *Platelet Aggregation Studies
    *Flow Cytometry
    *(Gene Sequencing

Block 3 (51 decks)

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