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Semester 3 - Infection > Session 9 - Immunocompromised Host > Flashcards

Session 9 - Immunocompromised Host Flashcards

1
Q

What is the importance of immuno-defiency?

A
  • Immunodeficiency is associated with an increase in the frequency and severity of infections
    • Immunodeficiency is associated with autoimmune diseases and malignancy
    • Failure to recognize and diagnose leads to increased morbidity and mortality
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2
Q

Why is immunodeficiency considered to be subversive?

A

• Long gap between symptom onset and immunodeficiency

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3
Q

Define “immunocompromised”

A

• State in which the immune system is unable to respond appropriately and effectively ot infectious microorganisms

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4
Q

What are two types of defects involved in immunocompromised hosts?

A

Qualitative or quantitative defect of one or more components of the immune system

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5
Q

Give three components of innate immunity which could potentially go wrong?

A
  • Innate barriers
    • Phagocytes
    • Complement
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6
Q

Give three components of adaptive immunity which could potentially go wrong

A
  • B cell
    • Antibodies
    • T cells
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7
Q

Give four features of infections which come about as a result of immunocompromise?

A 
• SPUR
		○ S - Severe
		○ P - Persistent
		○ U - Unusual
		○ R - Reccurent
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8
Q

What are two types of immunodeficiency?

A
  • Primary

* Secondary

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9
Q

What is a primary immunodeficiency?

A

• Intrinsic defect
○ Single-gene disorder
○ Polygenic
○ Polymorphisms

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10
Q

What is a secondary immunodeficiency?

A

• Underlying disease or condition affecting immune components
○ Decreased production

Loss or catabolism

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11
Q

How is a primary immunodeficiency classified?

A

• By the part of the immune system which is damaged

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12
Q

What types of patients are primary immunodeficiency? (age and gender)

A
  • 80% patients <20 yrs

* 70% males (x-linked)

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13
Q

What factors can be affected in a primary immunodeficiency?

A

B cell (50%)
• T cell (30%)
• Phagocytes (18%)
• Complement (2%)

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14
Q

Name three important B cell deficiencies (primary immunodefiency)

A
  • Common variable immunodeficiency
    • IgA deficiency
    • Bruton’s disease
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15
Q

What is the most common type of primary immunodeficiency?

A
  • Common variable immunodeficiency

* Inability of B cells to mature into plasma cells

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16
Q

What does the immunoglobulin/cell levels of someone with B cell CVID look like?

A
  • IgG <5g/l

* IgA and IgM variable

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17
Q

What is the clinically defining feature of IgA deficiency

A
  • IgA <0.05g/l

* B cell unable to switch to IgA

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18
Q

what is the clinically defining feature of Bruton’s disease (3)

A
  • Impaired B cell development
    • IgG <2g/l
    • IgA undetectable
    • Low B cells
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19
Q

How do patients with primary immunodeficiency present?(5)

A
  • Recurrent upper and lower respiratory bacterial infection (bronchiectasis)
    • GI complications including infections
    • Arthropathies
    • Increased incidence of autoimmune disease
    • Increased incidence of lymphoma and gastric carcinoma
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20
Q

How are primary immuno-deficient patients treated? (4)

A
  • Prophylactic antibiotics
    • Immunoglobulin replacement therapy
    • Management of respiratory function

Avoid unnecessary exposure to radiation

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21
Q

What is immunoglobulin replacement therapy and what is its goal?

A
  • IgG >8g/l

* Replacement of immunoglobulin

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22
Q

What is immunoglobulin replacement therapy used to treat?

A

• CIVD

Bruton’s disease

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23
Q

Given two phagocyte deficiencys

A
  • Leukocyte Adhesion Deficiency (LAD)
    • Chronic granulomatous disease (CGD)

Cyclic neutropenia

24
Q

What occurs in Leukocyte Adhesion Deficiency?

A

• Phagocytes cannot adhere to endothelium

25
Q

What occurs in Chronic granulamatous disease?

A
  • Phagocytes can produce respiratory burs

* Granulomas form

26
Q

What is the presentation of someone with a phagocyte deficiency?

A
  • Prolonged and recurrent infection
    • Ulcers
    • Abscesses (granuloma)
    • Invasive aspergillosis
27
Q

What is the management of someone with phagocyte deficiency?

A
  • Prophylactic antibiotic
    • Interferon-g

Steroids

28
Q

How do you recognise someone with phagocyte deficiency?

A

ABSCESS

29
Q

Name three main T cell deficiencies

A
  • Di George deficiency

* Severe combined Immunodeficiency (SCID)

30
Q

What is DiGeorge syndrome?

A
  • Defect in thymus embryogenesis and incomplete development

* Characterised by lack of thymus

31
Q

Why is DiGeorge syndrome called CATCH-22 Syndrome

A 
CATCH 22 
	• Cardiac abnormalities
	• Abnormal faces
	• Thymic hypoplasia 
	• Cleft palate 
	• Hypocalcaemia
	• MORE SUSCEPTIBLE TO VIRAL AND FUNGAL INFECTIONS
32
Q

What is the genetic cause of Catch 22 syndrome/DiGeorge?

A

• chromosomal abnormalities

33
Q

What is the management of Di George syndrome?

A

• Neonatal cardiac surgery

supplement to correct hypocalcaemia

34
Q

What non-related medical treatment is prohibited in Di George syndrome

A

• Live vaccines

35
Q

What causes SCID?

A

• Stem cell defect in g chain used by many T cell receptors

Death of developing thymocytes

36
Q

What does SCID look like?

A
  • Failure to thrive
    • Protracted diarrhoea
    • Hepato-splenomegaly

Low lymphocyte count

37
Q

What is a short term management for SCID?

A
  • aggressive treatment of infections

* Prevention of new infections

38
Q

Give a long term treatment for SCID?

A

• Bone marrow transplant

Gene therapy

39
Q

Name one complement component deficiency

A
  • C1 inhibitor deficiency

* Hereditary angiooedema

40
Q

What are secondary immune deficiencies caused by?

A
  • Malnutritition
    • Infection
    • Liver diseases
    • Lymphoproliferative diseases
    • Drug induced neutropenia

Splenectomy

41
Q

Give three causes of asplenia

A
  • Infarction (SICKLE CELL DISEASE)
    • Trauma
    • Autoimmune
42
Q

Give three causes of neutropenia

A

• Bone marrow infiltration with malignancy

Chemotherapy - Cytotoxics and immunosupressants

43
Q

What is the management of neutropenia?

A

• Treat suspected neutropenic spesis as an acute medical emergency and offer empiric antibiotic therapy immediately

Asses patient’s risk of septic complications

44
Q

What is the standard presentation of an asplenic patient?

A

• Susceptibility to encapsulated bacteria
○ Haemophilus influenzae
○ Streptococcus pneumoniae

Neisseria meningitidis

45
Q

Why are asplenic patients susceptible to encapsulated bacteria?

A
  • Contains B cells which do not need T cell activation
    • Encapsulated bacteria difficult to break down and present
    • Spleen required to clear them
46
Q

What is OPSI?

A
  • Overwhelming post-splenectomy infection

* Causes sepsis and meningitis

47
Q

What is the mangement of an asplenic patient?

A
  • Penicillin prophylaxis
    • Immunisation against encapsulated bacteria
    • Patient information; Medic alter bracelet
48
Q

What are the three main immune functions of the spleen?

A 
• Removal of blood borne pathogens
		○ Encapsulated bacteria
	• Antibody production
		○ Acute response IgM production
		○ Long term protection IgG production
	• Splenic macrophages
		○ Removal of opsonized microbes 
		○ Removal of immune complexes
49
Q

Taking a history from a patien

A

Age - at presentation
– Sex
– Site(s) and frequency of infection(s)
– Type of organism(s)
• Viruses and bacteria -> T cell deficiency
• Bacteria and fungi -> B cell/granulocytes deficiency
– Sensitivity and type of treatment (surgery)
– Family history

50
Q

Give two general investigations of ID

A
  • FBC and differential

* Exclusion of secondary immunodeficiency

51
Q

Give four specific investigations for ID

A
  • Test of humoral antibodies
    • Tests for cell mediated immunity
    • Tests for phagocytic cells

Test for complement

52
Q

What do you test for in cell mediated immunity?

A

• IgG, IgA, IgM (+/- IgE)
• IgG1-4
subclasses
• IgG levels to specific previous vaccines
tetanus toxoid / HiB / pneumococcus
measles , mumps, rubella
• Measure antibody in response to “test” immunization

53
Q

Where is CRP produced?

A

Liver

54
Q

What is the role of CRP in the innate immune response?

A

CRP acts as an opsonin.

An opsonin binds to the microbial surface leading to enhanced attachment of phagocytes and clearance of microbes.

55
Q

i. What triggers the production of CRP?

A

Microbial toxins – e.g. endotoxin – triggers the production of cytokines by monocytes and macrophages. These in turn circulate in the blood to the liver where they stimulate the production of the acute phase proteins.

Semester 3 - Infection (14 decks)

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