10. Immunocompromised Host

Question 1

What is primary immunodeficiency (PID)?

Answer 1

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

Question 2

What is secondary immunodeficiency?

Answer 2

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

Question 3

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

Answer 3

"SPUR"
Severe
Persistant
Unusual - site or microorganism
Recurrent

Question 4

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

Answer 4

2

Question 5

What are some common causes of PID?

Answer 5

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

Question 6

Which PID is caused by phagocytic defects?

Answer 6

Chronic granulomatous disease - defective NADH oxidase

Question 7

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

Answer 7

Age of onset

Type of microbes and sites of infection

Question 8

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

Answer 8

T cell or phagocytic defect

Question 9

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

Answer 9

B cell/Antibody or phagocyte

Question 10

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

Answer 10

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

Question 11

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

Answer 11

B cell/antibody
Complement
or Secondary immune deficiency

Question 12

What type of infections are characteristic of complement deficiency?

Answer 12

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

Question 13

What type of infections are characteristic of phagocyte defects?

Answer 13

Skin/mucous infections
Deep seated infections
Invasive fungal infections

Question 14

Which fungal infection is associated with phagocyte defects?

Answer 14

Aspergillosis

Question 15

What inheritance pattern does chronic granulomatous disease show?

Answer 15

Autosomal recessive

Question 16

What infections are associated with antibody deficiency?

Answer 16

Sinorespiratory infections 
Arthopathies
GI infections
Malignancies
Autoimmunity

Question 17

Which type of PID is giardia lambia associated with?

Answer 17

Antibody

Question 18

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

Answer 18

Bruton’s disease

Question 19

What are the signs of T cell defects?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

T cell

Question 22

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

Answer 22

B cell and granulocytes

Question 23

What supportive treatment can you give to patients with PID?

Answer 23

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

Question 24

What specific treatment can you give to patients with PID?

Answer 24

Regular immunoglobulin therapy (IVIG or SCIG)

Question 25

What type of PID is HSCT used for?

Answer 25

Severe combined immunodeficiency (SCID)

Question 26

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

Answer 26

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

Question 27

Which PID conditions is immunoglobulin replacement therapy used for?

Answer 27

CVID Bruton's disease Hyper-IgM syndrome

Question 28

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

Answer 28

``` Liver diseases Malnutrition Splenectomy Infection (HIV) Lymphoproliferative diseases ```

Question 29

What is the immune function of the spleen?

Answer 29

- Antibody production from B cells - Splenic macrophages remove opsonised microbes - Removal of blood borne pathogens and encapsulated bacteria

Question 30

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

Answer 30

Encapsulated - Haemophilus influenzae Strep. pneuomia Neisseria meningitidis

Question 31

How can asplenic patients be managed to avoid overwhelming infection?

Answer 31

- Life-long penicillin prophylaxis | - Immunisation against encapsulated bacteria

Question 32

What is an OPSI?

Answer 32

Overwhelming post-splenectomy infection | - Sepsis or meningitis usually

Question 33

How does chemotherapy alter a patients susceptibility to infections?

Answer 33

Increased risk of infections: 1. Neutropenia 2. Damage to mucosal barriers 3. Vascular catheters

Question 34

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

Answer 34

Protein-losing conditions: Nephropathy Enteropathy Burns

Question 35

Where is aspergillus usually found?

Answer 35

Ubiquitous in dust, soil and the air

Question 36

When can aspergillus become pathogenic?

Answer 36

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

Question 37

What is the most common site of infection of aspergillus?

Answer 37

Lung

Question 38

What type of infection is aspergillus?

Answer 38

Fungal

Question 39

How is aspergillus infection treated?

Answer 39

Amphotericin

Question 40

Why might aspergillus not be detected on a blood culture?

Answer 40

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

Question 41

What group of viruses does Varicella-zoster belong to?

Answer 41

Herpes-simplex

Question 42

What primary infection does varicella-zoster cause?

Answer 42

Chicken pox

Question 43

What is the structure of varicella zoster?

Answer 43

dsDNA | Enveloped

Question 44

How is varicella zoster transmitted?

Answer 44

Via respiratory droplets

Question 45

Outline how varicella zoster virus invades and multiplies within hosts.

Answer 45

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

Question 46

Explain how varicella zoster viruses causes characteristic vesicular rashes?

Answer 46

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

Question 47

How long is the incubation period of varicella zoster?

Answer 47

15 days - while multiplying in the liver and spleen

Question 48

How long after initial exposure does the characteristic rash appear?

Answer 48

14-21 days

Question 49

When is a person infected with varicella zoster most infectious?

Answer 49

1-2 days before rash appears

Question 50

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

Answer 50

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

Question 51

How does varicella zoster cause shingles later in life?

Answer 51

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

Question 52

What is characteristic of shingles?

Answer 52

Dermatomal rash

Question 53

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

Answer 53

Acyclovir in immunocompromised patients as infection can be severe