Haem 6 - Abnormal white cell counts

Question 1

Explain how neutrophil differentiation and maturation occurs

Answer 1

Myeloblast –> promyelocyte –> myelocyte –> metamyelocyte –> band cells –> neutrophil

Myeloid precursors are not normally seen in peripheral blood

Question 2

When is it not uncommon to see myeloid precursors?

Answer 2

In sepsis patients

Question 3

How are cell numbers controlled in haematopoiesis

Answer 3

Cytokines influence differentiation and proliferation.

Erythroid - controlled by erythropoietin

Lymphoid - controlled by IL-2

Myeloid - controlled by G-CSF and M-CSF

Question 4

What are the causes of abnormal WBC

Answer 4

Increased WBC:

1. Increased cell production - Reactive (infection/inflammation), Malignant (leukaemia/myeloproliferative)
2. Increased cell survival - failure of apoptosis

Decreased WBC:
1. Decreased cell production - impaired bone marrow function, B12/Folate deficiency, bone marrow failure (aplastic anaemia/post chemo/metastatic cancer/haematological cancer)

2. Decreased cell survival - immune breakdown

Question 5

What happens when there are haematopoietic cancers

Answer 5

Immature and mature cells are released into the circulation

Normally, should just be mature cells

Question 6

What are the 2 causes of eosinophilia

Answer 6

1. Reactive - normal haemopoiesis. Stimulated by inflammation, infection, increased cytokine production (as a result of a distant tumour, e.g.)
2. Primary (malignant) - abnormal haemopoiesis (autonomous cell growth). Caused by cancers of haemopoietic cells, leukaemia (myeloid / lymphoid, both chronic and acute), myeloproliferative disorders

Question 7

In chronic myeloid leukaemia, where does the mutation occur?

Answer 7

Mutation occurs at the GM-CFC phase - causes massive proliferation of myeloid cells beyond this point

Question 8

How to investigate a raised WCC?

Answer 8

1. History and examination
2. Hb and platelet count
3. Automated differential
4. Examine blood film
5. Are all 3 lineages (RBC, WBC, platelet) affected or just WBC?
6. Is it only one type of WBC affected?

Question 9

How to suspect leukaemia and acute leukaemia?

Answer 9

If immature cells in the blood film

If ONLY immature cells with low Hb and low platelets - acute leukaemia

Question 10

Why might lymphocytes be elevated?

Answer 10

1. Viral infections
2. Chronic lymphocytic leukaemia

In leukaemia, neutrophils don’t have granules (whereas there are granular neutrophils In infection)

Question 11

Describe neutrophils

Answer 11

1. Present in bone marrow, blood and tissues
2. Lifespan of 2-3 days in tissues
3. 50% neutrophils - marginated - stuck onto wall of damaged vessel (hence not counted in RBC)

Question 12

Give 3 instances when neutrophilia can develop

Answer 12

Minutes - demmargination

Hours - early release from bone marrow

Days - increased production

Question 13

What are the causes of neutrophilia

Answer 13

1. Infection
2. Tissue inflammation
3. Physical stress
4. Adrenaline
5. Corticosteroids
6. Underlying neoplasia
7. Malignant neutrophilia (myeloproliferative disorders, chronic myeloid leukaemia)

Question 14

How can we deduce a viral infection

Answer 14

Low neutrophil count but other features of infection

Question 15

What are some reactive causes of eosinophilia

Answer 15

1. Parasitic infection
2. Allergic disease (e.g. asthma, RA, polyarteritis, pulmonary eosinophilia)
3. Neoplasms (e.g. Hodgkins, non-hodgkins lymphoma)
4. Hypereosinophilic syndrome

Question 16

Give a genetic cause of eosinophilia

Answer 16

Malignant Chronic Eosinophilic Leukaemia (PDGFR fusion gene)

• very rare
• can be detected by FISH (fluorescent)

Question 17

Hodgkins disease can cause eosinophilia - how can you tell if someone has Hodgkins disease?

Answer 17

1. Increased mediastinal mass on CXR

2. IL-5 secretion - stimulating reactive eosinophilia

Question 18

When is monocytosis seen

Answer 18

Rare - seen in certain chronic infections and primary haematological disorders

e.g. TB, Brucella, typhoid

Viral - cmv, Varicella zoster

Sarcoidosis, chronic myelomonocytic leukaemia (MDS- myelodysplastic syndrome)

Question 19

How can we distinguish lymphocytosis types

Answer 19

If mature cells - reactive to infection, primary disorder

If immature cells - primary disorder (leukaemia/lymphoma)

Question 20

What is a typical blood film of Chronic lymphoid leukaemia

cells may look similar if autoimmune / inflammatory conditions

Answer 20

Mature lymphocytes - big nucleus with little cytoplasm

Oligo

Question 21

Describe the appearance of immature lymphoblasts

Answer 21

Immature lymphoblasts = much larger than mature lymphoblasts. Can also see nucleolus in immature lymphoblasts.

Can be seen in acute lymphoblastic leukaemia

Question 22

What is secondary (reactive) cause of lymphocytosis

Answer 22

Polyclonal response to infection, chronic inflammation or underlying malignancy

Question 23

What is a primary cause of lymphocytosis

Answer 23

Monoclonal lymphoid proliferation - all cells will look the same - mutated cell expanding and making clones of itself

e.g. CLL

Question 24

Name some causes of reactive lymphocytosis

Answer 24

1. Infection (e.g. EBV, CMV, toxoplasma, etc)
2. Autoimmune disorders
3. Neoplasia
4. Sarcoidosis

Question 25

Describe mononucleosis syndrome

Answer 25

"Atypical lymphocyte" - reactive looking lymphocyte

Question 26

Mononucleosis syndrome is typical of?

Answer 26

Glandular fever

Question 27

If you see a high White cell count, and find reactive looking lymphocytes, you can be reassured that it is a?

Answer 27

Reactive, infection-induced lymphocytosis

Question 28

Describe glandular fever

Answer 28

1. EBV infection of B lymphocytes via CD21 receptor 2. Infected B cell proliferates and expresses EBV associated antigens 3. Cytotoxic T-lymphocyte response 4. Acute infection resolved - results in lifelong sub-clinical infection 5. Glandular fever - more common in young people

Question 29

Lymphocytosis in elderly is more likely to be caused by?

Answer 29

Chronic lymphocytic leukaemia - mature lymphocytes (and maybe smear cells).

Question 30

When responding to infection, you get a polyclonal response. Lightchains in antibody can be which ?

Answer 30

Kappa or lambda If polyclonal expansion in B cells, 50/50 split in kappa and lambda But if monoclonal expansion - you get Light chain restriction - B cells produce only kappa or only lambda So if MONOCLONAL - kappa/lambda restriction - NOT response to infection

Question 31

Explain gene rearrangement in lymphocytosis

Answer 31

Immunoglobulin genes (Ig) and T cell receptors (TCR) genes undergo recombination in antigen stimulated B/T cells In PRIMARY MONOCLONAL Proliferation - all daughter cells carry identical configuration of Immunoglobulin gene, or TCR gene - can be detected by southern blot analysis

Question 32

2 likely causes of eosinophilia?

Answer 32

1. Parasitic infection - schistosomiasis 2. Underlying lymphoma (Hodgkins / NHL) 3. Allergic autoimmune disorder

Question 33

If kappa / lambda restriction, what should I do

Answer 33

To distinguish further - test light chain restriction or test for T cell receptor arrangement If K/L restriction present, most likely to be chronic lymphocytic leukaemia

Question 34

Blood film features of CML

Answer 34

1. Myelocyte precursors (shouldn't be present normally) 2. No toxic granules present in neutrophils (would be present in infection) 3. Basophil seen 4. Expansion of myeloid cells