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Infection > 10. Immunocompromised Host > Flashcards

10. Immunocompromised Host Flashcards

1
Q

What is primary immunodeficiency (PID)?

A

Congenital immunodeficiency due to an intrinsic gene defect.
Could be missing protein missing cell or non-functional components.

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2
Q

What is secondary immunodeficiency?

A

Acquired immunodeficiency due to an underlying disease or treatment.
Could be due to decreased production or increased loss of immune components.

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3
Q

What acronym is used to identify when to suspect an immunodeficiency?

A 
"SPUR"
Severe
Persistant
Unusual - site or microorganism
Recurrent
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4
Q

How many warning sites must be demonstrated to be diagnosed with PID?

A

2

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5
Q

What are some common causes of PID?

A
  1. Antibody deficiency
  2. Common variable immunodeficiencies (CVID)
  3. Combined T and T cell
  4. Phagocytic defects
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6
Q

Which PID is caused by phagocytic defects?

A

Chronic granulomatous disease - defective NADH oxidase

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7
Q

What information can be useful when trying to diagnose a PID?

A

Age of onset

Type of microbes and sites of infection

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8
Q

Presentation <6 months is likely to be defect in what?

A

T cell or phagocytic defect

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9
Q

Presentation 6 months- 5 years is likely to be a defect in what?

A

B cell/Antibody or phagocyte

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10
Q

What do antibody defects usually only present after around 6 months?

A

Maternal IgG antibodies are in the circulation for the first 6 months

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11
Q

Presentation >5 years is likely to be a defect in what?

A

B cell/antibody
Complement
or Secondary immune deficiency

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12
Q

What type of infections are characteristic of complement deficiency?

A 
Meningitis, sepsis, arthritis (C5-C9)
Pyogenic infections (C3)
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13
Q

What type of infections are characteristic of phagocyte defects?

A

Skin/mucous infections
Deep seated infections
Invasive fungal infections

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14
Q

Which fungal infection is associated with phagocyte defects?

A

Aspergillosis

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15
Q

What inheritance pattern does chronic granulomatous disease show?

A

Autosomal recessive

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16
Q

What infections are associated with antibody deficiency?

A 
Sinorespiratory infections 
Arthopathies
GI infections
Malignancies
Autoimmunity
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17
Q

Which type of PID is giardia lambia associated with?

A

Antibody

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18
Q

What X-linked disease causes defects in B cell development?

A

Bruton’s disease

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19
Q

What are the signs of T cell defects?

A

Failure to thrive
Deep skin and tissue accesses
Opportunistic infections
Death if not treated

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20
Q

What other immune cell will be affected by T cell defects?

A

B cells - T cells provide cytokine signals that stimulate isotype switching to IgG, so IgG levels will decrease.

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21
Q

Are viral and fungal infections associated with T or B cell deficiency?

A

T cell

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22
Q

Are bacterial and fungal infections associated with T or B cell deficiency?

A

B cell and granulocytes

23
Q

What supportive treatment can you give to patients with PID?

A
  • Prophylactic microbials
  • Nutritional support - Vitamins A+D
  • Avoid live attenuated vaccines
  • Treat infections promptly and aggressively
24
Q

What specific treatment can you give to patients with PID?

A

Regular immunoglobulin therapy (IVIG or SCIG)

25
Q

What type of PID is HSCT used for?

A

Severe combined immunodeficiency (SCID)

26
Q

What comorbidies are patients with PID at an increased risk of developing?

A

Malignancies - avoid non-essential exposure to radiation
Autoimmune diseases
Organ damage

27
Q

Which PID conditions is immunoglobulin replacement therapy used for?

A

CVID
Bruton’s disease
Hyper-IgM syndrome

28
Q

What can cause secondary immunodeficiency due to decreased production of immune components?

A 
Liver diseases 
Malnutrition
Splenectomy 
Infection (HIV)
Lymphoproliferative diseases
29
Q

What is the immune function of the spleen?

A
  • Antibody production from B cells
  • Splenic macrophages remove opsonised microbes
  • Removal of blood borne pathogens and encapsulated bacteria
30
Q

Which bacteria are asplenic patients at a higher risk of infection by?

A

Encapsulated -
Haemophilus influenzae
Strep. pneuomia
Neisseria meningitidis

31
Q

How can asplenic patients be managed to avoid overwhelming infection?

A
  • Life-long penicillin prophylaxis

- Immunisation against encapsulated bacteria

32
Q

What is an OPSI?

A

Overwhelming post-splenectomy infection

- Sepsis or meningitis usually

33
Q

How does chemotherapy alter a patients susceptibility to infections?

A

Increased risk of infections:

  1. Neutropenia
  2. Damage to mucosal barriers
  3. Vascular catheters
34
Q

What can cause secondary immunodeficiency due to increased loss or catabolism of immune components?

A

Protein-losing conditions:
Nephropathy
Enteropathy
Burns

35
Q

Where is aspergillus usually found?

A

Ubiquitous in dust, soil and the air

36
Q

When can aspergillus become pathogenic?

A

Rarely in normal hosts, but can cause disease in immunodeficient hosts.

37
Q

What is the most common site of infection of aspergillus?

A

Lung

38
Q

What type of infection is aspergillus?

A

Fungal

39
Q

How is aspergillus infection treated?

A

Amphotericin

40
Q

Why might aspergillus not be detected on a blood culture?

A

Tend to remain isolated and form cavities rather than entering the blood stream

41
Q

What group of viruses does Varicella-zoster belong to?

A

Herpes-simplex

42
Q

What primary infection does varicella-zoster cause?

A

Chicken pox

43
Q

What is the structure of varicella zoster?

A

dsDNA

Enveloped

44
Q

How is varicella zoster transmitted?

A

Via respiratory droplets

45
Q

Outline how varicella zoster virus invades and multiplies within hosts.

A

Initial infection in respiratory mucos
Spreads to lymph nodes, where it replicated
Progeny spread to liver and spleen where multiply further.

46
Q

Explain how varicella zoster viruses causes characteristic vesicular rashes?

A

Endothelial and skin epithelial cells become infected, causing virus-containing vesicular rashes

47
Q

How long is the incubation period of varicella zoster?

A

15 days - while multiplying in the liver and spleen

48
Q

How long after initial exposure does the characteristic rash appear?

A

14-21 days

49
Q

When is a person infected with varicella zoster most infectious?

A

1-2 days before rash appears

50
Q

Can it be caught by contact with vesicular fluid in rashes?

A

No, respiratory droplet transmission, cells must re-infect mucosa at the end of incubation period

51
Q

How does varicella zoster cause shingles later in life?

A

Viruses enter cutaneous neurones and migrate to ganglia, where they remain in latent state.
They can become reactivated to cause shingles.

52
Q

What is characteristic of shingles?

A

Dermatomal rash

53
Q

How can shingles be treated? Which patients are likely to need treatment?

A

Acyclovir in immunocompromised patients as infection can be severe

Infection (15 decks)

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