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HAEMOPHILIA, BLEEDING DISORDERS, TRANSFUSION - MUHS 2nd MBBS Pathology

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Q2. BLEEDING DISORDERS - Definition, Classification, Screening Lab Tests

Definition

• Blood vessels (vascular integrity)
• Platelets (primary haemostasis)
• Coagulation factors (secondary haemostasis)
• Fibrinolytic system

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NORMAL HAEMOSTASIS - Overview (Easy Exam Diagram)

INJURY TO VESSEL
        |
        ▼
PRIMARY HAEMOSTASIS          SECONDARY HAEMOSTASIS
(Platelet Plug)              (Coagulation Cascade)
        |                           |
Vasoconstriction          Intrinsic + Extrinsic Pathways
        |                           |
Platelet adhesion (vWF)    Common Pathway → Fibrin Clot
        |                           |
Platelet aggregation       Thrombin → Fibrinogen → Fibrin
        |                           |
    Platelet plug           Stable Fibrin Clot
        |___________________________|
                    |
             STABLE HAEMOSTATIC PLUG

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COAGULATION CASCADE (Must-Draw Exam Diagram)

EXTRINSIC PATHWAY        INTRINSIC PATHWAY
(Tissue Factor / FVII)   (FXII → FXI → FIX → FVIII)
           \                    /
            \                  /
             ↘                ↙
           COMMON PATHWAY
           FX → FV → Prothrombin (FII)
                          ↓
                       Thrombin
                          ↓
           Fibrinogen → Fibrin (loose)
                          ↓
                    FXIII → Stable Fibrin Clot

PT measures: Extrinsic + Common (Factors VII, X, V, II, Fibrinogen)
APTT measures: Intrinsic + Common (Factors XII, XI, IX, VIII, X, V, II, Fibrinogen)

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Classification of Bleeding Disorders

• Hereditary: Hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu)
• Acquired:
  • Vitamin C deficiency (Scurvy)
  • Henoch-Schonlein Purpura (allergic vasculitis)
  • Infections (meningococcemia, rickettsia)
  • Senile purpura
  • Cushing's syndrome (steroid excess)

1. Quantitative (Thrombocytopenia) - low platelet count
2. Qualitative (Thrombocytopathies)
   • Glanzmann's thrombasthenia (defect in GPIIb/IIIa)
   • Bernard-Soulier syndrome (defect in GPIb)
   • Uraemia, aspirin use

• Hereditary:
  • Haemophilia A (Factor VIII deficiency)
  • Haemophilia B / Christmas disease (Factor IX deficiency)
  • von Willebrand disease (vWF deficiency)
• Acquired:
  • Vitamin K deficiency (affects Factors II, VII, IX, X)
  • Liver disease (decreased synthesis of all factors)
  • Disseminated Intravascular Coagulation (DIC)
  • Anticoagulant therapy (warfarin, heparin)

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Screening Laboratory Tests for Bleeding Disorders

Prolonged BT + Normal PT + Normal APTT → Platelet/Vascular disorder
Prolonged PT + Normal APTT           → Extrinsic pathway defect (Factor VII)
Normal PT + Prolonged APTT           → Intrinsic pathway defect (Haemophilia A/B)
Prolonged PT + Prolonged APTT        → Common pathway defect or DIC or liver disease

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Q1. HAEMOPHILIA (Haemophilia A)

Definition

Genetics & Inheritance

         Carrier Mother (X^h X)  x  Normal Father (X Y)
                    |
         ___________↓___________
        |      |         |      |
      X^h X   X X      X^h Y   X Y
    (Carrier) (Normal) (AFFECTED) (Normal)

• Gene located on X chromosome (Xq28)
• Males affected; females are carriers
• ~30% cases arise from new mutations

Types of Haemophilia

Severity Classification

Clinical Features

• Haemarthrosis (bleeding into joints) - most characteristic; affects knees, ankles, elbows
• Chronic haemophilic arthropathy (repeated bleeds → joint destruction)
• Deep tissue haematomas (muscle, retroperitoneal)
• Haematuria
• Intracranial haemorrhage (major cause of death)
• Excessive bleeding after cuts, dental extractions, surgery
• NO petechiae, NO mucosal bleeding (these suggest platelet disorders)

Lab Findings (High-yield)

HAEMOPHILIA A LAB PROFILE:
- Platelet count        → NORMAL
- Bleeding Time (BT)    → NORMAL
- Prothrombin Time (PT) → NORMAL
- APTT                  → PROLONGED ✓ (corrected by mixing with normal plasma)
- Factor VIII assay     → DECREASED
- Factor IX             → Normal

Pathology - Haemophilic Arthropathy (Histology)

REPEATED HAEMARTHROSIS
         ↓
Iron deposits in synovium (haemosiderin) → Brown discolouration
         ↓
Synovial hypertrophy & chronic inflammation
         ↓
Cartilage erosion (pannus formation)
         ↓
Subchondral cyst formation, periarticular fibrosis
         ↓
ANKYLOSIS (end-stage)

• Villous hyperplasia
• Haemosiderin deposits in synoviocytes and macrophages
• Chronic inflammatory infiltrate (lymphocytes, plasma cells)
• Fibrous tissue proliferation

Treatment

• Factor VIII concentrate (recombinant or plasma-derived)
• Cryoprecipitate (rich in Factor VIII, vWF, fibrinogen)
• DDAVP (desmopressin) - releases vWF and Factor VIII from endothelium in mild haemophilia
• Gene therapy (emerging)

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Q7. PROTHROMBIN TIME (PT) - Principle and Causes of Increased PT

Principle of PT Test

PRINCIPLE OF PT TEST:

Patient citrated plasma
         +
Tissue thromboplastin (Tissue Factor + Phospholipid)
         +
Calcium chloride (CaCl2)
         ↓
Clot formation → TIME RECORDED = PT

Activates:    Factor VII → X → V → II (Prothrombin) → Thrombin → Fibrin

Normal PT: 11-13.5 seconds
INR (International Normalized Ratio) = (Patient PT / Control PT)^ISI
Normal INR: 0.8-1.2
Therapeutic INR (on warfarin): 2.0-3.0

Causes of Increased (Prolonged) PT

• Hereditary Factor VII deficiency
• Warfarin therapy (most common clinical cause - inhibits Vitamin K-dependent factors II, VII, IX, X)
• Early liver disease (Factor VII has shortest half-life of ~6 hours)

• Liver disease (hepatitis, cirrhosis) - decreased synthesis
• Disseminated Intravascular Coagulation (DIC) - consumption
• Vitamin K deficiency (biliary obstruction, malabsorption, neonates)
• Warfarin therapy

• Afibrinogenaemia
• Dysfibrinogenaemia

Summary Table - PT vs APTT

FACTOR DEFICIENCY    →    PT    |    APTT    |   DIAGNOSIS
Factor VII only      → ↑↑PT   |  Normal    | Factor VII def / Early Warfarin
Factors VIII/IX/XI   → Normal  |  ↑↑APTT   | Haemophilia A/B
Factors X, V, II     → ↑PT    |  ↑APTT     | Common pathway defect
All factors          → ↑PT    |  ↑APTT     | Liver disease / DIC

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Q8. CAUSES OF THROMBOCYTOPENIA - Enumeration

Definition

• <50,000/µL: Increased post-traumatic bleeding risk
• <20,000/µL: Spontaneous bleeding risk
• <5,000/µL: Spontaneous severe bleeding (petechiae, purpura, intracranial haemorrhage)

Classification and Causes

1. Generalised Bone Marrow Failure
   • Aplastic anaemia (congenital - Fanconi; acquired - drugs, radiation, idiopathic)
   • Bone marrow infiltration: Leukaemia, disseminated carcinoma, myelofibrosis, lymphoma
2. Selective Impairment of Platelet Production
   • Drug-induced: Alcohol, thiazides, cytotoxic drugs (chlorambucil, methotrexate)
   • Infections: Measles virus, HIV infection
3. Ineffective Megakaryopoiesis
   • Megaloblastic anaemia (Vit B12 / folate deficiency)
   • Paroxysmal Nocturnal Haemoglobinuria (PNH)

1. Immunologic Destruction
   • Autoimmune: Immune Thrombocytopenic Purpura (ITP), SLE, antiphospholipid syndrome
   • Alloimmune: Post-transfusion purpura, Neonatal alloimmune thrombocytopenia
   • Drug-associated: Quinidine, Heparin (HIT), Sulfa compounds
2. Non-immunologic Destruction
   • Disseminated Intravascular Coagulation (DIC)
   • Thrombotic Thrombocytopenic Purpura (TTP) - ADAMTS13 deficiency
   • Haemolytic Uraemic Syndrome (HUS) - Shigatoxin-producing E.coli
   • Microangiopathic Haemolytic Anaemias (MAHA)

• Hypersplenism (any cause of splenomegaly: portal hypertension, malaria, lymphoma)
• Normally spleen holds 30% of platelet pool; in hypersplenism up to 90% sequestered

• Multiple blood transfusions for massive blood loss (stored blood lacks viable platelets)

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ITP - Histopathology (Bone Marrow - Easy to Draw)

BONE MARROW IN ITP:

Normal haematopoiesis
+ INCREASED MEGAKARYOCYTES (compensatory)
    - Megakaryocytes appear young/immature
    - No platelet budding seen (destruction is peripheral)

PERIPHERAL BLOOD:
    - Large platelets (megathrombocytes)
    - Normal/decreased platelet count
    - No RBC or WBC abnormality

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Q9. MAJOR FRACTIONS OF BLOOD - Utility; BLOOD COMPONENTS - Name Four

Major Fractions of Blood

WHOLE BLOOD
    |
    ├── CELLULAR ELEMENTS (45%)
    |       ├── RBCs (Erythrocytes)
    |       ├── WBCs (Leukocytes)
    |       └── Platelets (Thrombocytes)
    |
    └── PLASMA (55%)
            ├── Proteins (7%)
            |     ├── Albumin (60%)
            |     ├── Globulins (36%) → α, β, γ
            |     └── Fibrinogen (4%)
            ├── Water (90-92%)
            └── Dissolved substances
                  (glucose, electrolytes, lipids, hormones, waste)

Utility of Major Fractions

Four Blood Components (MUHS Exam Answer)

1. Packed Red Blood Cells (PRBCs)
   • Prepared by centrifugation of whole blood, removing plasma
   • Haematocrit 55-80%
   • Stored at 1-6°C, shelf life 42 days (with additive solution)
   • Used for: Anaemia, surgical blood loss
2. Platelet Concentrate (Random Donor Platelets / Single Donor Platelets)
   • Separated from whole blood by centrifugation or apheresis
   • Stored at 22°C with continuous agitation, shelf life 5 days
   • Used for: Thrombocytopenia, platelet dysfunction
3. Fresh Frozen Plasma (FFP)
   • Plasma frozen within 6-8 hours of collection; contains ALL coagulation factors
   • Stored at -18°C or below, shelf life 1 year
   • Used for: DIC, liver disease, warfarin reversal, Factor V/XI deficiency
4. Cryoprecipitate
   • Cold-insoluble precipitate formed when FFP is thawed at 4°C
   • Rich in: Factor VIII, von Willebrand factor, Fibrinogen (Factor I), Factor XIII, Fibronectin
   • Stored at -18°C, shelf life 1 year
   • Used for: Haemophilia A, vWD, fibrinogen deficiency, DIC

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Q3 & Q4. BLOOD TRANSFUSION REACTIONS - Complete Detailed Answer

Definition

Classification

TRANSFUSION REACTIONS
        |
        ├── IMMUNOLOGICAL
        |       ├── Acute (within 24 hrs)
        |       |     ├── Acute Haemolytic Transfusion Reaction (AHTR)
        |       |     ├── Febrile Non-Haemolytic Transfusion Reaction (FNHTR)
        |       |     ├── Allergic/Anaphylactic Reaction
        |       |     ├── TRALI (Transfusion-Related Acute Lung Injury)
        |       |     └── Hypotensive Reaction
        |       └── Delayed (after 24 hrs)
        |             ├── Delayed Haemolytic Transfusion Reaction (DHTR)
        |             ├── Transfusion-Associated Graft-vs-Host Disease (TA-GvHD)
        |             └── Post-Transfusion Purpura (PTP)
        |
        └── NON-IMMUNOLOGICAL
                ├── Transfusion-Associated Circulatory Overload (TACO)
                ├── Bacterial Contamination / Septic Reaction
                ├── Transfusion-Transmitted Infections (HIV, HCV, HBV)
                ├── Hyperkalaemia, Hypothermia
                └── Citrate toxicity (hypocalcaemia)

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1. ACUTE HAEMOLYTIC TRANSFUSION REACTION (AHTR) - Most Important

ABO-incompatible blood transfusion
            ↓
Preformed recipient IgM antibodies bind to donor RBC antigens
            ↓
Complement activation → Intravascular haemolysis (MAC complex)
            ↓
Release of haemoglobin, cytokines, bradykinin
            ↓
TRIAD: Haemoglobinemia + Haemoglobinuria + Hyperbilirubinaemia
            ↓
Shock → Acute Renal Failure → DIC → DEATH

• Fever, chills, rigors (FIRST signs)
• Chest and back/flank pain (haemolysis)
• Haemoglobinuria (red/brown urine)
• Hypotension, tachycardia
• Diffuse bleeding (secondary DIC)
• Oliguria/Anuria (acute tubular necrosis)
• In anaesthetized patients: unexplained hypotension, haemoglobinuria are the only signs

• Decreased Hb
• Decreased haptoglobin
• Elevated LDH
• Haemoglobinuria
• Positive Direct Antiglobulin Test (DAT / Coombs test)
• Incompatible crossmatch

• STOP transfusion immediately
• Maintain urine output (IV saline, furosemide)
• Treat hypotension (dopamine)
• Manage DIC if present
• Notify blood bank

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2. FEBRILE NON-HAEMOLYTIC TRANSFUSION REACTION (FNHTR)

Donor leukocytes in stored blood
        ↓
React with recipient's anti-HLA antibodies (WBC antibodies)
        ↓
Cytokine release (IL-1, IL-6, TNF-α) during storage
        ↓
FEVER ≥38°C or ≥1°C rise from baseline

• Fever, chills (within 1-6 hrs of transfusion)
• No haemolysis
• Must exclude AHTR before labeling as FNHTR

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3. ALLERGIC / ANAPHYLACTIC TRANSFUSION REACTION

Plasma proteins in transfused blood
        ↓
IgE-mediated hypersensitivity (Type I)
        ↓
Mast cell/basophil degranulation
        ↓
Histamine release → Urticaria → Anaphylaxis

Special case: Anti-IgA antibodies in IgA-deficient patients → Anaphylaxis

• Mild: Urticaria, pruritus, flushing
• Severe (Anaphylaxis): Bronchospasm, hypotension, angioedema, stridor, shock

• Mild: Antihistamines, slow/stop transfusion
• Severe: Epinephrine (adrenaline), corticosteroids, H1/H2 blockers
• Prevention in IgA-deficient patients: Use IgA-deficient donor blood or washed RBCs

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4. TRALI (Transfusion-Related Acute Lung Injury)

Donor anti-HLA (class I/II) or anti-HNA antibodies (from multiparous females)
        ↓
Bind to recipient neutrophils → Neutrophil activation
        ↓
Pulmonary endothelial damage
        ↓
Increased vascular permeability → Pulmonary oedema

• Acute respiratory distress (dyspnoea, hypoxia)
• Bilateral pulmonary infiltrates on CXR (bilateral white-out)
• Hypotension
• Fever
• Normal cardiac function (ECHO shows no left heart failure)

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5. TACO (Transfusion-Associated Circulatory Overload)

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6. DELAYED HAEMOLYTIC TRANSFUSION REACTION (DHTR)

Previous sensitisation to non-ABO RBC antigens (Rh, Kidd, Duffy, Kell)
        ↓
Low titre anamnestic antibody (below detection threshold at crossmatch)
        ↓
Re-exposure: Antibody rises rapidly (secondary immune response)
        ↓
IgG-coated RBCs → Extravascular haemolysis (spleen)

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7. TRANSFUSION-ASSOCIATED GvHD (TA-GvHD)

Immunocompetent donor T-lymphocytes in transfused blood
        ↓
Engraft in immunosuppressed recipient
        ↓
Recognise host tissues as foreign
        ↓
Attack: Skin, Liver, Gut, Bone Marrow

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8. BACTERIAL CONTAMINATION / SEPTIC REACTION

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TRANSFUSION REACTIONS - Summary Table (MUHS High-Yield)

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QUICK EXAM-DRAW DIAGRAMS SUMMARY

Haemophilia Inheritance Pattern

X^H X (Carrier mother) x XY (Normal father)
        ↓
25% Normal female, 25% Carrier female, 25% Normal male, 25% AFFECTED male

ITP Bone Marrow Histology (Easy Draw)

Bone marrow biopsy cross-section:
- Normal fat cells (adipocytes) - circles
- Normal erythroid/myeloid precursors
- INCREASED MEGAKARYOCYTES (large cells with multi-lobed nucleus) ← KEY FINDING
- Peripheral blood: low platelets but LARGE platelets (megathrombocytes)

Coagulation Waterfall

XII→XI→IX↘
           X→V→II→Thrombin→Fibrin
     VII↗
         (PT tests this arm: VII,X,V,II,I)
         (APTT tests: XII,XI,IX,VIII,X,V,II,I)

Blood Component Preparation (Easy to Draw)

WHOLE BLOOD
    ↓ Centrifuge (slow spin)
PLATELET-RICH PLASMA  +  PACKED RBCs
    ↓ Centrifuge (fast spin)
PLATELET CONCENTRATE  +  PLASMA
                          ↓ Freeze within 6 hrs
                         FFP
                          ↓ Thaw at 4°C, collect precipitate
                        CRYOPRECIPITATE

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KEY HIGH-YIELD MNEMONICS FOR MUHS EXAM

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