The Immunocompromised Host

Question 1

Define an Immunocompromised Host

What is the cause?

Answer 1

A state in which the immune system is unable to respond appropriately and effectively to infectious microorganisms

Defect in 1/ more components of the immune system

Question 2

Compare the 2 types of Immunocompromised state

Answer 2

Primary Immunodeficiency (congenital);
- Due to gene defect

Secondary Immunodeficiency (acquired);
- Due to an underlying disease/ treatment

Question 3

What are 3 ways a gene defect leads to immunodeficiency (Primary)

Answer 3

• Missing protein
• Missing cell
• Non functional components of immune system

Question 4

What are 2 ways an underlying disease/ treatment leads to immunodeficiency (Secondary)

Answer 4

• Decreased production/ function of immune components
• Loss/ Increased catabolism of immune components

(Main cause of secondary immunodeficiency is malnutrition)

Question 5

What are 4 things to consider when suspecting the possibility of immunodeficiency

Answer 5

• Age
• Sex
• Site of infection
• Type of microbe

Question 6

When should you suspect immunodeficiency?

Answer 6

When infections are SPUR;

Severe
Persistent
Unusual
Recurrent

Question 7

What are 5 warning signs of Primary Immunodeficiency (PID) in Children?

Answer 7

• Family history of PID
• Need of IV Antibiotics to clear infections
• Persistent thrush in mouth/ fungal infection on skin
• Recurrent, deep skin or organ abscesses
• Failure of an infant to gain weight/ grow normally

Question 8

What are 5 warning signs of Primary Immunodeficiency (PID) in Adults?

Answer 8

• Family history of PID
• Need of IV Antibiotics to clear infections
• Persistent thrush in mouth/ fungal infection on skin
• Recurrent, deep skin or organ abscesses
• Chronic diarrhoea with weight loss

Question 9

What are 3 limitations of the ‘10 warning signs’ of PID (Primary Immunodeficiency)

Answer 9

• Lack of population based evidence
• Patients present differently
• Patients can present with non infectious manifestations

Question 10

What is Severe Combined Immunodeficiency (SCID)

Answer 10

A PID, characterised by defects in both T and B lymphocytes

Question 11

What is Common Variable Immunodeficiency (CVID)?

Answer 11

A PID, characterised by recurrent infections and low antibody levels (IgM, IgA, IgG)

Question 12

What is Bruton’s disease?

Answer 12

An X-linked PID, characterised by a defect in B cell development and a reduced immunoglobulin production

Question 13

What are 2 causes of immunodeficiency involving antibody defects?

Answer 13

• Defect in B cell development

- Defect in antibody production

Question 14

What are 2 causes of immunodeficiency involving T cell defects?

Answer 14

• T cell defects

- Combined B and T cell defects

Question 15

What are 3 causes of immunodeficiency involving phagocytic defects?

Answer 15

• Defects in respiratory burst
• Defect in fusion of lysosome/ phagosomes
• Defect in neutrophil production and chemotaxis

Question 16

What is Chronic Granulomatous disease?

Answer 16

An X-linked PID where the Superoxide radical can’t be made, so pathogens can’t be phagocytosed.

(Increased susceptibility to bacteria and fungi)

Question 17

What defects are suggested by PID symptom onset;

1. <6 months old
2. > 6 months and <5 years old
3. > 5 years old

Answer 17

1. Suggests T cell or Phagocyte defect
2. Suggests B cell antibody or Phagocyte defect
3. Suggests B cell/ Antibody/ Complement defect or SID

(T cells are vital so a defect would present before 6 months of age)

Question 18

What are 2 methods of management of PIDs

Answer 18

• Supportive treatment

- Specific treatment

Question 19

What is the goal of Immunoglobulin Replacement Therapy (IRT)? (It is a life long treatment)

What are 2 formulations used?

What are 3 conditions it can be used to treat?

Answer 19

To get serum IgG above 8g/L

• IvIg
• ScIg (young patients)
• CVID
• Bruton’s disease (XLA)
• Hyper IgM Syndrome

Question 20

List 5 causes of Decreased production of immune components, leading to SIDs

Answer 20

• Malnutrition (most common)
• Infection
• Liver disease
• Haematological malignancies
• Splenectomy

Question 21

List 2 causes of Increased loss of immune components, leading to SIDs

Answer 21

• Burns

- Protein losing conditions

Question 22

In patients with haematological abnormalities, what are 3 causes of increased infection susceptibility?

Answer 22

• Chemotherapy induced neutropenia
• Chemotherapy induced damage to mucosal barriers
• Vascular catheters

Question 23

How do you treat Febrile Neutropenia?

Answer 23

• Immediate antibiotic therapy (Tazocin)

- Asses risk of sepsis