Haematology - MPN

Question 1

Components and functions of lymphatic system

Answer 1

Components:

• Lymph
• Lymphatic vessels
• lymphatic trunks (Lumbar, intestinal, bronchomediastinal, subclavian, jugular)
• lymphatic ducts (thoracic duct, right lymphatic duct)
• Lymphatic organs (Primary - BM, Thymus; Secondary - LN, Spleen, MALT, GALT, Tonsils)

Functions:

1. Excess interstitial fluid drainage
2. Immune response
3. Dietary lipid and lipid-soluble vitamin transport and absorption

Question 2

Spleen

• Functions (4)
• General structure

Answer 2

Function:

• Hematopoiesis in fetal life
• Filter circulating blood: remove old/ abnormal RBC
• Immune response: Antibody production, antigenic stimulation
• Blood storage

General structure:

• Fibrous capsule with trabeculae extension
• Red pulp (periphery): Splenic sinuses and splenic cords (Billroth cords) remove old RBC and drain into splenic veins
• White pulp (central) - Follicles, periarterial lymphatic sheath (PALS), Marginal zone for proliferation and antigenic stimulation of B cells, APCs in marginal zone

Question 3

Main causes of splenomegaly *****

Answer 3

Hemolysis

• Hereditary causes: spherocytosis, thalassaemia intermedia, HbH disease
• Autoimmune haemolytic anaemia

Infection:

• Malaria
• TB, infective endocarditis
• EBV, CMV, HIV

Immune-mediated:
- Felty syndrome (RA)

Vascular congestion

Malignant Infiltration

Storage disease: Gaucher disease

Question 4

Causes of vascular congestion causing splenomegaly

Answer 4

• Blockage of flow and blood pooling in red pulp
• Cirrhosis or non-cirrhotic portal hypertension

Post-hepatic:

• Budd-Chiari syndrome
• IVC obstruction
• Right heart failure

Intra-hepatic
- Liver cirrhosis

Pre-hepatic

• Portal vein thrombosis
• Splenic vein thrombosis

Question 5

Malignancies that cause splenomegaly

Answer 5

1. Chronic Leukaemia: CML, CLL
2. Acute leukaemia: ALL
3. Myeloproliferative neoplasm:
   - Primary myelofibrosis
   - Polycythaemia vera
   - Essential thrombocythaemia
4. Lymphoma

Question 6

History taking for Splenomegaly

Answer 6

Basic particulars: Age, gender, race

Splenomegaly compressive S/S: Abdominal fullness, Early Satiety

Haematological malignancy S/S:

• Pancytopenia S/S: thrombocytopenia and bleeding tendency, anaemia S/S, frequent infections …etc
• Bone pain, pathological fractures

Residence and travel history (infective causes)

Constitutional symptoms (malignancies)

Family history (storage diseases)

Question 7

Physical exams for splenomegaly

Answer 7

General:
Anemia: Pallor, jaundice, Tachycardia, cyanosis
Thrombocythemia: bruising, deep-seated bleeding, mucocutaneous bleeding in gum/ mouth
Constitutional/ CA: Lymphadenopathy (Epitrochlear nodes, Axillary nodes, Cervical nodes), cachexia/ muscle wasting, bony tenderness

Specific Etiologies:
- Infections: Rash, retinal lesions (CMV, toxoplasmosis)
- Autoimmune diseases: arthralgia due to Felty’s syndrome (due to RA), Gout (due to MPD), Connective tissue disease
- Leukemia: e.g. testicular/ mediastinal mass (ALL)

Splenomegaly:
- Size below costal margin
- Confirm spleen: LUQ mass, moves down with respiration, cannot get above it, Dull on percussion, splenic notch present
- Associated hepatomegaly, lymphadenopathy
- Stigmata of liver disease

Question 8

Ddx splenomegaly by size

Answer 8

Massive: CML, Myelofibrosis

Moderate: Portal hypertension, haematological malignancies

Minimal: Haemolytic anaemia (Thal. intermedia, HbH disease), Autoimmune cytopenia (ITP, AIHA), Infective causes

Question 9

D/dx splenomegaly by incidence

Answer 9

Common:
→ Haematological malignancy, eg. lymphoma, leukaemia, MPN
→ Portal hypertension, eg. cirrhosis, splenic v. obstruction
→ Haemolytic anaemia, eg. thal intermedia, HBH disease, AIHA, hereditary spherocytosis

Rare:
→ Chronic inflammatory or A/I disease
→ Infections, eg. IE, schistosomiasis, malaria

Extremely uncommon:
→ Certain CAs,eg. splenic lymphoma with villous lymphocytes, hairy cell leukaemia
→ Certain infections, eg. hepatosplenic candidiasis, chronic malaria infection
→ Storage diseases

Question 10

First line investigations for splenomegaly

Answer 10

Investigations:

• CBC with diff.
• Clotting profile
• LFT
• HbsAg
• Imaging of abdomen: USG, CT, PET-CT

Question 11

Post-splenectomy/ Hyposplenism features on PBS

Answer 11

Howell-Jolly bodies + nucleated RBC

Question 12

Outline the transition of normal hematopoietic stem cell to myeloid malignancies

Answer 12

Question 13

AML

• Genetic cause
• Peripheral blood changes
• BM exam findings

Answer 13

• Two-hit mutations: Somatic mutation of TET2, IDH1/ IDH2 confers proliferative advantage and impairs differentiation
• Pancyotpenia due to BM infiltration, Variable WBC levels, Myeloid blast cells
• BM infiltration by leukaemic blasts, reduced normal haemopoietic cells

Question 14

MPN

• Genetic cause
• Peripheral blood changes
• BM exam findings
• Examples

Answer 14

• Gain-of-fx mutations in pro-growth signalling
  Eg. BCR-ABL1, JAK2, MPL, CALR
• Increase cell count in 1 or more lineages, non-dysplastic cells
• Hypercellular with ↑progenitor cells, Effective haemopoiesis with normal differentiation
• Examples:

CML (BCR-ABL Positive)

Polycythaemic vera, Essential thrombocythaemia, Primary myelofibrosis, CNL, CEL (BCR-ABL negative)

Question 15

MDS

• Genetic cause
• Peripheral blood changes
• BM exam findings

Answer 15

• Loss-of-fx mutations in terminal differentiation
• Pancytopenia, Morphology dysplastic
• Hypercellular marrow, Ineffective haemopoiesis with aberrant differentiation, N/↑ blasts <20%

Question 16

MDS/ MPN

• Genetic cause
• Peripheral blood changes
• BM exam findings

Answer 16

• Mixture of gain-of-function mutation in pro-growth signaling and loss-of-function in terminal differentiation
• Increase cell count, morphology dysplastic
• Hypercellular marrow, Features of aberrant differentiation present

Question 17

MPN

• Definition
• Key features

Answer 17

Definition:
- clonal disease involving pluripotential haematopoietic stem cell of myeloid lineage
- Proliferation of all three haematopoietic lineages viz. erythroid, myeloid and megakaryocytic
(CBC may only show proliferation in one lineage doesn’t mean that the other lineages are normal)
- Potential to progress to myelofibrosis and blastic transformation

Key features:
□ Increased circulating cells
□ Hypercellular marrow
□ Absence of myelodysplastic features (cf MPN/MDS)

Question 18

Complications of MPN

Answer 18

Transformation into AML

Other transformation: into MDS, develop myelofibrosis

Thrombohaemorrhagic complications: most pronounced in PV and ET

Overwhelming Post-splenectomy Infection (OPSI) medical emergency

Question 19

CML

• Key genetic mutation
• Defining features
• AML risk

Answer 19

BCR-ABL1 (95% a/w t(9;22)

Presence of Philadelphia chromosome (karyotype) or BCR-ABL1 (FISH) or fusion mRNA transcript (RT-PCR)

> 90% if untreated

Question 20

Polycythaemia vera

• Key genetic mutation
• Defining features
• AML risk

Answer 20

Cause:
somatic mutation in Janus kinase 2 (JAK2) in HSC: ↑proliferation of RBC series ± granulocyte and platelet series
Mutation: JAK2 V617F (95-97%), JAK2 exon 12 (3%)

(1) Otherwise unexplained polycythaemia (↑Hb or ↑Hct)
(2) Hypercellular marrow showing trilineage growth and megakaryocytic proliferation
(3) JAK2 V617F/exon 12 mutation

AML risk:
10% at 10y
25% at 25y

Question 21

Polycythaemia vera

• Clinical definition
• Epidemiology
• Clinical features

Answer 21

Definition: RBC mass >125% that expected for body mass and gender

• Male >16.5g/dL
• Female >16g/dL

Demographics:

• median age 60y
• M>F = 2:1
• RARELY a/w FHx

Clinical features: Hyperviscosity, Hypervolaemia and Hypermetabolism

• Hyperviscosity: Headache, dizziness, loss of concentration, SOB
• Aquagenic pruritis**
• Erythromelalgia *(burning pain in hands/feet with color change) due to mircrovascular thrombosis
• Thrombohaemorrhagic: Arteriovenous thrombosis, Bleeding **
• Facial plethora (Ruddy cyanosis)

Others:

• Retinal venous engorgement
• GI symptoms: mucosal erosions, PUD
• Transient visual symptoms

Question 22

Polycythaemia vera:

• Diagnostic criteria
• Major ddx to exclude
• Treatment
• Transformations

Answer 22

Major diagnostic criteria
1. High RBC volume by Hb or Hct
2. BM biopsy show hypercellularity for age with trilineage growth (panmyelosis) including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes
3. JAK2 mutation: either V617F or exon 12 mutation
Minor criteria: serum EPO below reference

Rule out secondary causes of polycythaemia, exclude high EPO state:
- Chronic hypoxia e.g. COPD
- Abnormal EPO secretion e.g. Hepatoma
Rule out ET, EPO receptor mutations

Treatment:

• Hyperviscosity symptoms: Venesection/ Therapeutic phlebotomy + Cytoreduction by Hydroxyurea, peg-IFN-α or busulphan (suppress erythropoiesis)
• Thromboprophylaxis: Low-dose aspirin

Transformations:

• AML
• 10% Myelofibrosis (Post-PV myelofibrosis)

Question 23

Primary myelofibrosis

• Key genetic mutation
• Defining features
• AML risk

Answer 23

JAK2 (60-65%), CALR (20-25%), MPL (7%)

(1) Megakaryocytic proliferation/atypia ± myelofibrosis
(2) Any clonal mutation (JAK2, CALR, MPL, other clonal markers) or no other cause of reactive fibrosis
(3) Does not meet CML, PV, ET, MDS criteria

AML risk: 6-18%

Question 24

Essential throbocythaemia

• Key genetic mutation
• Defining features
• AML risk

Answer 24

JAK2 (60-65%), CALR (20-25%), MPL (3%)

(1) Thrombocytosis (PLT ≥450 × 109/L)
(2) Predominant megakaryocyte proliferation and no significant involvement of other lineages on BM
(3) Demonstration of JAK2, CALR or MPL mutation

AML risk: <5%

Question 25

Essential thrombocythaemia - Clinical definition - Epidemiology - Diagnostic criteria - Prognosis and transformations

Answer 25

Definition: sustained ↑platelet count (>450 ×109/L) due to megakaryocyte proliferation resulting in overproduction of platelets Demographics: median age 60y, peak at 30y for women, F>M = 2:1 Diagnostic criteria: 4 major or 3 major + 1 minor Major criteria: → Platelet count ≥450×10^9/L → BM biopsy: proliferation of mainly megakaryocyte lineage with ↑numbers of enlarged, mature megakaryocytes with hyperlobulated nuclei AND no significant left shift in neutrophil granuopoiesis or erythropoiesis and very rarely minor (G1) increase in reticulin fibres → Not meeting criteria for other myeloid neoplasms incl CML, PV, PMF, MDS → Demonstrate of JAK2, CALR or MPL mutation Minor criteria: → Demonstration of another clonal marker (ASXL1, EZH2, TET2, IDH1/IDH2, SRSF2, or SR3B1 mutation) OR no identifiable cause of thrombocytosis (eg, infection, inflammation, iron deficiency anemia) Median survival: 10-15 years Transformations: - Post-ET Myelofibrosis - AML

Question 26

Essential thrombocythaemia - Clinical presentation - Treatment

Answer 26

Clinical presentation: Asymptomatic: incidental finding Vasomotor symptoms due to microvascular thrombosis → Neurological: headache, lightheadedness, syncope, TIA → Acral symptoms: acral paraesthesia, erythromelalgia Mainly Arterial Thrombosis, eg. stroke, MI, superficial thrombophlebitis, DVT, PE, digital ischaemia Paradoxical haemorrhage with extreme thrombocytosis (>1000×109/L) and acquired vWD Treatment: Low-dose Aspirin Cytoreductive: Hydroxyurea, peg-IFNα-2a, platelet-pheresis Cardiovascular risk modification: smoking cessation, weight loss

Question 27

Myelofibrosis - subtypes and definitions

Answer 27

Acute myelofibrosis: - very rare form of AML - characterized by rapid onset of severe BM fibrosis - a/w fever, **pancytopenia, tear-drop RBCs and leucoerythroblastic picture with no splenomegaly** Secondary myelofibrosis: - from **previous PV or ET** **Other chronic myeloid disorders** - CML, MDS, MDS/MPN, PV...etc Misc. haematological disorders: uncommon, eg. hairy cell leukaemia, lymphoma, multiple myeloma Non-haematological disorders: rare, eg. metastatic BM infiltration, A/I disorders, 2o hyperPTH

Question 28

Primary myelofibrosis - Defining features - Epidemiology - Pathogenesis

Answer 28

Features: - unexplained progressive **generalized reactive BM fibrosis** - development of **extramedullary haematopoiesis in spleen and liver** - Non-functional marrow Epidemiology - median age 67y, Increase incidence with aging Pathogenesis: NOT a neoplasm of fibroblasts - **sporadic mutation in JAK2, CALR, MPL**→ activation of growth factor signaling in megakaryocytes → **proliferation of megakaryocytic** lineage → elaboration of platelet-derived growth factor **(PDGF) and TGT-B** - PDGF and TGT-B Stimulate **Reactive fibroblast proliferation** → BM fibrosis **Leucoerythroblastic picture (left-shifting) + tear-drop RBCs, high reticulin** - HSC move to extramedullary sites for haematopoiesis

Question 29

primary myelofibrosis Clinical course and S/S, CBC in each stage

Answer 29

Clinical course: divided into two phases 1. Cellular (prefibrotic) phase (pre-PMF): megakaryocyte atypia only without significant fibrosis S/S: - Mild anaemia only with Leukocytosis/thrombocytosis - no blasts, no splenomegaly 2. Fibrotic phase (overt PMF): significant marrow fibrosis S/S: - pancytopenia (marrow replacement) with leukoerythroblastic blood picture - Progressive anaemia with abnormal morphology: dacrocytes (teardrop RBCs), anisopoikilocytosis, polychromasia - hepatosplenomegaly (extramedullary haematopoiesis) - high LDH - Dry tap on BM aspirate

Question 30

Primary myelofibrosis Clinical presentation Treatment Prognosis

Answer 30

Constitutional: severe fatigue (50-70%), low-grade fever, bone pain, night sweats, LOW/A Anaemic S/S and thrombohaemorrhage events Massive splenomegaly: hallmark of PMF Hepatomegaly (40-70%) ± portal hypertension (increase intrahepatic obstruction from extramedullary hematopoiesis, increase splanchnic flow) Musculoskeletal abnormalities: Osteosclerosis, Periostitis Treatment: - Ruxolitinib (JAK1/2 kinase inhibitor) - Splenectomy - Allogeneic HSCT Prognosis: Worst non-CML MPN median survival 6y

Question 31

Overwhelming post-splenectomy infection (OPSI) - Causative pathogen - Prevention methods

Answer 31

Causative agents: Encapsulated bacteria Prevention: - Pre-operative vaccination against streptococcal pneumoniae, Haemophilus influenzae, Neisseria meningitidis - Post-op antibiotic prophylaxis with penicillin - Patient education