Hematopathology II: WBC

Question 1

What are the key structural and functional roles of the spleen?

Answer 1

• Filters aged/damaged RBCs in red pulp
• Triggers immune response via white pulp (lymphoid follicles)
• Stores mononuclear phagocytes and lymphoid cells

Question 2

What is leukopenia and which white blood cell is most commonly affected?

Answer 2

a decrease in circulating white blood cells, most commonly due to low neutrophils (called neutropenia)

Question 3

What causes decreased production of neutrophils?

Answer 3

Chemotherapy or radiation
Aplastic anemia
Leukemia

Question 4

What are the two main causes of neutropenia?

Answer 4

1. Production Defects – poor or ineffective granulocyte production.
2. Peripheral Destruction/Utilization – increased loss or use of neutrophils

Question 5

What is agranulocytosis?

Answer 5

a severe form of neutropenia, with almost no neutrophils left in the blood or bone marrow (ANC <500/µL)

Question 6

What is the most common cause of agranulocytosis?

Answer 6

Drug toxicity, often from medications that damage bone marrow or immune-mediated drug reactions

Question 7

What defines neutropenia?

Answer 7

An absolute neutrophil count (ANC) less than 1500 cells/µL (calculated as WBC × % neutrophils)

Question 8

What are common causes of inadequate/ineffective neutrophil production?

Answer 8

• Aplastic anemia, marrow infiltration (e.g., leukemia)
• Drugs/toxins (chemo, certain antibiotics)
• Megaloblastic anemia, myelodysplasia
• Congenital causes, e.g. cyclic neutropenia (ELANE gene, ANC <200), kostmann syndrome

Question 9

What causes accelerated neutrophil removal?

Answer 9

• Autoimmune diseases (e.g., SLE)
• Splenomegaly (neutrophil sequestration)
• Overwhelming infections (increased usage)

Question 10

What are the risks and treatments for severe neutropenia?

Answer 10

• Infection risk increases when ANC <500/µL
• Treatment includes: Control infections, Stop harmful drugs, G-CSF to boost marrow production

Question 11

What is lymphopenia and what are its common causes?

Answer 11

2nd most common type of leukopenia with an absolute lymphocyte count <1000 cells/µL
- Common causes include: Advanced HIV infection, Glucocorticoids or cytotoxic drug use, Autoimmune diseases, Malnutrition, Some viral infections

Question 12

What is leukocytosis and what causes it?

Answer 12

an increased white blood cell (WBC) count, caused by:
- increased production in bone marrow
- increased release from marrow stores
- decreased margination
- decreased tissue extravasation

Question 13

What are common causes of neutrophilia (neutrophil count > 7800/μL)?

Answer 13

• infections
• medications
• tissue necrosis
• inflammation
• tumors
• other (stress, seizures, smoking etc)

Question 14

What is a leukemoid reaction?

Answer 14

WBC count > 50,000/μL due to causes other than leukemia with majority being mature neutrophils with an increase in immature neutrophils, mainly caused by infections (C. diff) and G-CSF medications

Question 15

What defines lymphocytosis in adults?

Answer 15

An absolute lymphocyte count > 4000 cells/μL

Question 16

What are common causes of lymphocytosis?

Answer 16

• Infections (viral like EBV, CMV, hepatitis A; or bacterial like B. pertussis)
• Chronic immune stimulation (e.g., TB, brucellosis)
• Lymphoproliferative disorders

Question 17

What are reactive lymphocytes and where are they seen?

Answer 17

lymphocytes with large and smudgy chromatin, nucleoli (maybe), pale-grey blue cytoplasm with a ballerina skirt appearance
- seen in EBV infections

Question 18

What infections are small and large lymphocytes seen in?

Answer 18

• Small mature lymphocytes → Seen in Bordetella pertussis
• Large granular lymphocytes → Seen in HIV, rheumatoid arthritis, and large granular lymphocyte leukemia

Question 19

What causes infectious mononucleosis and how is it diagnosed?

Answer 19

• caused by Epstein-Barr Virus (EBV)
• diagnosed by Monospot test (detects IgM heterophile antibodies) and serologic testing for EBV capsid antigen

Question 20

What cell types and symptoms are seen in mononucleosis?

Answer 20

Reactive CD8+ T-cells (Downey cells) that resemble monocytes causing symptoms like sore throat, swollen tonsils, fatigue, lymphadenopathy, fever

Question 21

What defines monocytosis?

Answer 21

Absolute monocyte count > 1000 cells/μL

Question 22

What are common causes of monocytosis?

Answer 22

• Chronic infections (e.g., tuberculosis)
• Autoimmune disorders (e.g., lupus)
• Inflammatory bowel diseases (e.g., ulcerative colitis)
• Other infections: endocarditis, rickettsiosis, malaria
• Myeloid neoplasms

Question 23

What defines eosinophilia?

Answer 23

Eosinophils >500 cells/μl

Question 24

What are the common causes of eosinophilia?

Answer 24

• Allergies (asthma, hay fever)
• Parasites
• Drug reactions
• Skin diseases
• Collagen vascular diseases
• Malignancies (e.g., Hodgkin lymphoma)
• Addison’s disease

Question 25

What defines basophilia?

Answer 25

Basophils >200 cells/μl

Question 26

What are common causes of basophilia?

Answer 26

- Allergic conditions (asthma) - Myeloproliferative neoplasms (CML, polycythemia vera) - Chronic inflammatory diseases (TB, UC, RA)

Question 27

What is reactive lymphoid hyperplasia?

Answer 27

enlarged lymph nodes from antigenic stimulation of lymphoid tissue that can be chronic OR acute

Question 28

What is acute lymphoid hyperplasia?

Answer 28

acute infection involving neutrophils leading to tender, swollen and red lymph nodes that may form abscesses and show signs of necrosis

Question 29

What is chronic lymphoid hyperplasia?

Answer 29

chronic immune stimulation involving reactive B (follicular hyperplasia) or T (paracortical hyperplasia) cell zones leading to firm, non-tender lymph nodes seen in HIV and RA

Question 30

What are the zones in normal lymph node architecture?

Answer 30

- Cortex (B-cell zone): Lymphoid follicles, germinal centers - Paracortex (T-cell zone): Between follicles - Medulla: Sinuses and medullary cords - Vessels: Afferent lymphatics, efferent lymphatics, arteries/veins