STEP 1 — MCQs (NO answers here)

MCQ 1 — Definition and Importance

Hypercoagulability is:

a. A low tendency of blood to clot

b. An abnormally high tendency of blood to clot, often due to altered coagulation factors

c. Abnormal platelet count only

d. Always due to vessel wall injury

e. Only seen in arterial thrombosis

MCQ 2 — Venous vs Arterial

Hypercoagulability is MOST strongly associated with:

a. Venous thrombosis

b. Arterial thrombosis only

c. Intracardiac thrombosis only

d. Capillary microthrombi only

e. Only with trauma

MCQ 3 — Types of Hypercoagulability

The alterations predisposing to thrombosis can be grouped into:

a. Primary (genetic) and secondary (acquired)

b. Congenital and infectious

c. Platelet and endothelial

d. Nutritional and traumatic

e. Mechanical and autoimmune

MCQ 4 — Common Inherited Causes

The most frequent primary (inherited) hypercoagulable states are due to mutations in:

a. Fibrinogen and factor XIII

b. Factor V and prothrombin genes

c. Factor XII and prekallikrein

d. Protein S and antithrombin genes only

e. Factor VII and tissue factor

MCQ 5 — Factor V Leiden Frequency

The factor V Leiden mutation is carried by approximately:

a. 0.1% of the general population

b. 2%–15% of whites, up to ~60% in recurrent DVT

c. 50% of all ethnic groups

d. Only patients with cancer

e. Only patients with SLE

MCQ 6 — Mechanism of Factor V Leiden

Factor V Leiden increases thrombosis risk because:

a. Factor V cannot bind fibrinogen

b. It becomes resistant to proteolysis by protein C

c. It cannot bind calcium

d. It increases t-PA levels

e. It activates platelets directly

MCQ 7 — Risk Magnitude in Factor V Leiden

Risk of venous thrombosis in factor V Leiden:

a. No increase in heterozygotes

b. Fivefold in heterozygotes and about 50-fold in homozygotes

c. Only increased in women

d. Only increases with age >70

e. Only increased during infection

MCQ 8 — Prothrombin Gene Variant

The common prothrombin gene mutation (G→A in 3′-UTR):

a. Decreases prothrombin transcription

b. Has no clinical significance

c. Increases prothrombin transcription and about threefold venous thrombosis risk

d. Only affects arterial thrombosis

e. Causes thrombocytopenia

MCQ 9 — Homocysteine

Raised homocysteine is associated with:

a. Only venous thrombosis

b. Only atherosclerosis

c. Arterial and venous thrombosis and atherosclerosis

d. Only microangiopathy

e. Only hemorrhage

Marked elevations may result from:

a. Iron deficiency

b. Cystathionine β-synthetase deficiency

c. Factor XII deficiency

d. Protein C deficiency

e. Vitamin B12 excess

MCQ 10 — Rare Inherited Deficiencies

Inherited deficiencies of antithrombin III, protein C, or protein S typically present with:

a. Arterial stroke in infancy

b. Venous thrombosis and recurrent thromboembolism in adolescence or early adult life

c. Only bleeding disorders

d. Isolated thrombocytopenia

e. Only superficial thrombophlebitis in old age

MCQ 11 — When to Suspect Inherited Thrombophilia

Inherited causes should be considered particularly in:

a. Patients >80 years with DVT

b. Young patients (<50 years) with venous thrombosis, even if acquired risk factors exist

c. Only those with cancer

d. Only pregnant women

e. Only those with arterial MI

MCQ 12 — Acquired Hypercoagulability: Mechanisms

Acquired (secondary) hypercoagulability can be due to:

a. Stasis and vascular injury (e.g., trauma, cardiac failure)

b. Hypotension alone

c. Only low fibrinogen

d. Only thrombocytopenia

e. Only vitamin C deficiency

MCQ 13 — Estrogen-Related Hypercoagulability

Hypercoagulability with oral contraceptives and pregnancy is mainly due to:

a. Decreased hepatic synthesis of clotting factors

b. Increased synthesis of coagulation factors and reduced antithrombin III

c. Reduced estrogen levels

d. Increased protein C synthesis

e. Increased t-PA secretion

MCQ 14 — Cancer-Associated Hypercoagulability

In disseminated cancers, hypercoagulability is largely due to:

a. Bone marrow failure

b. Release of procoagulant tumor products such as mucin

c. Reduced platelet production

d. Massive fibrinolysis

e. Direct destruction of antithrombin

MCQ 15 — Age, Smoking, Obesity

Hypercoagulability with age is attributed to:

a. Increased t-PA

b. Increased platelet aggregation and reduced PGI2 release

c. Decreased thromboxane A2

d. Increased protein C

e. Decreased PAI

Smoking and obesity:

a. Have no effect on coagulation

b. Promote hypercoagulability by poorly understood mechanisms

c. Cause only thrombocytopenia

d. Cause isolated factor VIII deficiency

e. Always cause DIC

MCQ 16 — HIT Syndrome Mechanism

Heparin-induced thrombocytopenia (HIT) syndrome is characterized by:

a. Autoantibodies against fibrin only

b. Autoantibodies against heparin–platelet factor 4 complexes → platelet activation and thrombocytopenia

c. Autoantibodies that block thrombin generation

d. Autoantibodies that neutralize tissue factor

e. Autoantibodies against albumin

MCQ 17 — HIT Clinical Paradox

HIT results in:

a. Bleeding tendency with no thrombosis

b. A prothrombotic state despite heparin therapy and low platelet counts

c. Only isolated anemia

d. Only fibrinolysis

e. Only venous stasis without clots

MCQ 18 — Anti-Phospholipid Antibody Syndrome: Clinical Picture

Anti-phospholipid antibody syndrome can present with all EXCEPT:

a. Recurrent thromboses

b. Repeated miscarriages

c. Cardiac valve vegetations

d. Thrombocytopenia

e. Isolated hemophilia A

MCQ 19 — Organs and Complications in APS

Depending on vascular beds, anti-phospholipid syndrome can cause:

a. Pulmonary embolism, pulmonary hypertension, stroke, bowel infarction, renovascular hypertension

b. Only epistaxis and bruising

c. Only DIC

d. Only portal vein thrombosis

e. Only intracranial hemorrhage

MCQ 20 — Fetal Loss Mechanism in APS

Fetal loss in anti-phospholipid antibody syndrome is most likely due to:

a. Massive uterine artery thrombosis only

b. Antibody-mediated interference with trophoblast growth and placentation

c. Maternal anemia

d. Fetal infection

e. Isolated uterine atony

MCQ 21 — Renal Lesion in APS

A characteristic renal manifestation of anti-phospholipid antibody syndrome is:

a. Nephrotic syndrome due to minimal change disease

b. Renal microangiopathy with multiple capillary and arterial thromboses

c. Renal amyloidosis

d. Polycystic kidney disease

e. Simple renal cysts

MCQ 22 — Misleading Name “Lupus Anticoagulant”

In vitro, anti-phospholipid antibodies:

a. Accelerate coagulation

b. Interfere with phospholipid-dependent tests and inhibit coagulation

c. Have no effect

d. Only activate t-PA

e. Only shorten clotting times

In vivo they:

a. Are purely anticoagulant

b. Cause a hypercoagulable state

c. Have no clinical effect

d. Only cause bleeding

e. Only cause vasodilation

MCQ 23 — False-Positive Syphilis Test

Anti-phospholipid antibodies can cause a false-positive syphilis test because:

a. Syphilis antigens are identical to thrombin

b. The standard syphilis assay uses cardiolipin-containing antigen that cross-reacts

c. Syphilis damages endothelium

d. APS always coexists with syphilis

e. They activate complement

MCQ 24 — Primary vs Secondary APS

Secondary anti-phospholipid antibody syndrome is defined as:

a. APS occurring in pregnancy only

b. APS in patients with a well-defined autoimmune disease such as SLE

c. APS without any autoimmune features

d. APS following trauma

e. APS associated only with infections

MCQ 25 — APS in Normal Individuals

Anti-phospholipid antibodies:

a. Are always pathological

b. Are found in 5%–15% of apparently normal individuals

c. Are never seen in healthy people

d. Always cause DVT

e. Always cause fetal loss

STEP 2 — ANSWERS + SHORT EXPLANATIONS

MCQ 1 — b

Hypercoagulability = abnormally high tendency to clot, usually from coagulation factor alterations.

MCQ 2 — a

Most important for venous thrombosis, less frequent cause of arterial/intracardiac thrombosis.

MCQ 3 — a

Divided into primary (genetic) and secondary (acquired).

MCQ 4 — b

Most common inherited: mutations in factor V (Leiden) and prothrombin gene.

MCQ 5 — b

Factor V Leiden in 2%–15% of whites, and up to ~60% in recurrent DVT.

MCQ 6 — b

Leiden mutation → factor V resistant to proteolysis by protein C → loss of an important anticoagulant control.

MCQ 7 — b

Heterozygotes: ~5-fold risk; homozygotes: up to 50-fold risk of venous thrombosis.

MCQ 8 — c

Prothrombin G→A (3′-UTR) → increased transcription → ~3-fold increased venous thrombosis risk.

MCQ 9 — c / b

Raised homocysteine → arterial + venous thrombosis + atherosclerosis.

Marked elevation: cystathionine β-synthetase deficiency.

MCQ 10 — b

Inherited AT III, protein C, protein S deficiency → venous thrombosis and recurrent thromboembolism, often in adolescence/early adult life.

MCQ 11 — b

Consider inherited causes in young (<50 yr) venous thrombosis, even with acquired risk factors.

MCQ 12 — a

Acquired states: stasis/vascular injury (e.g., cardiac failure, trauma), plus other triggers.

MCQ 13 — b

OCPs and pregnancy: ↑ hepatic synthesis of clotting factors, ↓ antithrombin III.

MCQ 14 — b

Disseminated cancers: release procoagulant tumor products (e.g., mucin).

MCQ 15 — b

With age: ↑ platelet aggregation and ↓ PGI2 release.

Smoking/obesity → hypercoagulability by unknown mechanisms.

MCQ 16 — b

HIT: autoantibodies to heparin–PF4 complexes, binding platelets and endothelium → activation + consumption.

MCQ 17 — b

Despite low platelets and heparin therapy, HIT → strong prothrombotic state.

MCQ 18 — e

APS: recurrent thromboses, miscarriages, valve vegetations, thrombocytopenia; not hemophilia A.

MCQ 19 — a

APS complications: PE, pulmonary hypertension, stroke, bowel infarction, renovascular hypertension.

MCQ 20 — b

Fetal loss: due to antibody-mediated interference with trophoblast growth/placentation, not simply thrombosis.

MCQ 21 — b

Renal lesion: renal microangiopathy with multiple capillary and arterial thromboses → renal failure.

MCQ 22 — b / b

In vitro: antibodies interfere with phospholipid → inhibit coagulation (lupus “anticoagulant”).

In vivo: produce hypercoagulable state.

MCQ 23 — b

Standard syphilis test uses cardiolipin-containing antigen → cross-reacts with anti-phospholipid antibodies → false positive.

MCQ 24 — b

Secondary APS = APS in setting of autoimmune disease e.g., SLE.

Primary APS = no other autoimmune disease.

MCQ 25 — b

Antiphospholipid antibodies present in 5%–15% of normal individuals → necessary but not sufficient for full syndrome.

STEP 3 — HIGH-YIELD NOTES (EXAM-READY)

Hypercoagulability (Thrombophilia)

1. Core Concept

Hypercoagulability = increased tendency to form clots.

Mainly contributes to venous thrombosis, less commonly arterial or intracardiac thrombosis.

Causes fall into two categories:

• Primary (inherited)
• Secondary (acquired)

2. Primary (Inherited) Hypercoagulability

Most common causes involve Factor V and prothrombin gene mutations.

A. Factor V Leiden Mutation (Most Common)

• Found in 2–15% of whites.
• Found in ≈60% of recurrent DVT patients.
• Mutation → Factor V becomes resistant to Protein C inactivation.
• Loss of this key anticoagulant mechanism → thrombosis risk ↑.

Risk:

• Heterozygotes → 5× ↑ risk
• Homozygotes → 50× ↑ risk

B. Prothrombin Gene Mutation (G20210A)

• Single nucleotide change (G→A) in 3′-UTR.
• Seen in 1–2% of population.
• Causes increased prothrombin levels → coagulation tendency ↑.

Risk: ~3× ↑ venous thrombosis.

C. Hyperhomocysteinemia

• High homocysteine promotes arterial + venous thrombosis and atherosclerosis.
• Mechanism: formation of thioester linkages with proteins (e.g., fibrinogen).
• Severe elevations often due to cystathionine β-synthetase deficiency.

D. Rare Inherited Anticoagulant Deficiencies

• Antithrombin III deficiency
• Protein C deficiency
• Protein S deficiency

Clinical clue:

→ Recurrent venous thrombosis beginning in adolescence or early adulthood.

E. Importance of Gene–Environment Interaction

Even mild mutations (e.g., heterozygous Factor V Leiden) become dangerous when combined with:

• Pregnancy
• Oral contraceptives
• Prolonged immobilization
• Long-haul flights
• Surgery

Therefore: inherited causes should be considered in any patient <50 years old with venous thrombosis.

3. Secondary (Acquired) Hypercoagulability

Seen in many clinical settings.

Key mechanisms:

• Stasis (e.g., heart failure, trauma)
• Increased coagulation factor synthesis (e.g., estrogen states)
• Tumor procoagulants
• Platelet activation with age

A. Estrogen-Related States

1. Oral contraceptives
2. Pregnancy

Mechanism:

• ↑ hepatic synthesis of coagulation factors
• ↓ antithrombin III synthesis

→ Hypercoagulable state.

B. Malignancy (Trousseau Syndrome)

Especially adenocarcinomas producing mucin, a potent procoagulant.

Causes recurrent, migratory thromboses.

C. Advancing Age

• ↑ platelet aggregation
• ↓ endothelial PGI₂ (prostacyclin)

→ Prothrombotic shift.

D. Smoking and Obesity

Promote hypercoagulability by poorly understood mechanisms.

4. Two Clinically Important Acquired Syndromes

A. Heparin-Induced Thrombocytopenia (HIT) Syndrome

Occurs in up to 5% of patients on unfractionated heparin.(old types not lmwh)

Mechanism:

• Autoantibodies form against heparin + platelet factor 4 (PF4) complexes.
• Antibodies bind to platelets and endothelium →
• Platelet activation + aggregation
• Endothelial injury
• Paradoxical thrombosis despite low platelet count

LMWH has lower risk but still dangerous if antibodies already present.

B. Anti-Phospholipid Antibody Syndrome (APS)

Clinical features:

• Recurrent thrombosis (arterial + venous)
• Repeated miscarriages
• Cardiac valve vegetations
• Thrombocytopenia
• Renal microangiopathy → renal failure

Why pregnancy loss?

→ Antibodies injure trophoblasts → failure of placentation, not thrombosis.

Common manifestations:

• PE
• Pulmonary hypertension (from recurrent microemboli)
• Stroke
• Bowel infarction
• Renovascular hypertension

Pathophysiology

Despite the name, antibodies actually target proteins exposed by phospholipids, such as:

• β₂-glycoprotein I
• Prothrombin

In vivo: lead to hypercoagulability.

In vitro: interfere with phospholipid assays → prolonged clotting tests → “lupus anticoagulant” (misnomer).

Also cause false-positive syphilis tests (cardiolipin cross-reactivity).

Primary vs Secondary APS

• Primary APS: occurs without another autoimmune disease.
• Secondary APS: occurs in autoimmune diseases (e.g., SLE).

Therapy:

• Anticoagulation
• Immunosuppression

Note: APS antibodies are found in 5–15% of healthy individuals → not sufficient alone to cause syndrome.

5. Key Exam Takeaways

• Inherited = Factor V Leiden (most common), Prothrombin mutation, Homocysteine, Anticoagulant deficiencies
• Acquired = Estrogen states, malignancy, HIT, APS, age, smoking, obesity
• HIT = thrombocytopenia + paradoxical thrombosis
• APS = thrombosis + miscarriages + false-positive VDRL
• Always evaluate young (<50) thrombosis patients for inherited causes.