Infection: The immunocompromised host Flashcards Preview

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Flashcards in Infection: The immunocompromised host Deck (13)
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1
Q

What is an immunocompromised host?

A

A state in which the immune system is unable to respond effectively to infectious microorganisms due to a defect in one or more components of the immune system

2
Q

What are primary and secondary immunodeficiencies?

A

Primary immunodeficiency is congenital - due to either missing protein, missing cell or non functioning components.
Secondary immunodeficiency is acquired - due to a disease or treatment leading to loss of production/function of immune components, or catabolism of immune components.

3
Q

When should you suspect a pt has an underlying immunodeficiency?

A

Infections are SPUR:
Severe - need hospitalisation, life threatening
Persistant - fails to respond to usual treatment
Unusual - unusual site or unusual MO (opportunistic)
Recurrent

4
Q

What is the number 1 warning sign for a primary immunodeficiency?

A

A family history of PID

5
Q

What are the 3 most common primary immunodeficiencies?

A
  1. Common variable immunodeficiency (very low IgG + low IgA or IgM)
  2. IgA deficiency - usually asymptomatic
  3. IgG - usually asymptomatic
6
Q

What is SCID?

A

Severe combined immunodeficiency - there are very few T cells causing a B cell defect (don’t produce antibodies)

7
Q

What is the likely diagnosis if the pt is:
Less than 6 months
6m - 5 yrs
Over 5yrs

A

Onset before 6m suggest T cell or phagocyte defect
Onset between 6m and 5yrs suggests a B cell/antibody or phagocyte defect (first 6m had maternal IgG)
Onset over the age of 5 usually suggest B cell/ antibody/ complement deficiency or secondary immunodeficiency (90%)

8
Q

What are some of the supportive treatments for primary immunodeficiency diseases?

A

Prophylactic antimicrobials
Nutritional support - vit A and D good for immune system
Avoid live attenuated vaccines in severe PIDs eg SCID

9
Q

What are some of the specific treatments for primary immunodeficiency diseases?

A

Regular immunoglobulin theraoy

SCID: haematopoietic stem cell therapy

10
Q

Give some examples of secondary immune deficiencies

A
Most common is malnutrition 
HIV
Liver diseases (synthesises proteins)
Splenectomy 
Protein losing conditions eg nephropathy, enteropathy, crohns
11
Q

What is the management for asplenic pts?

A

Life long penicillin prophylaxis
Immunisation against encapsulated bacteria (H influenzae, strep pneumoniae, neisseria meningitidis)
Medic alert bracelets and cards

12
Q

What is the immune function of the spleen?

A

The spleen sensed encapsulated bacteria in the blood and the produces IgM and IgG. There are splenic macrophages which remove opsonised microbes - if they aren’t opsonised then they can be removed.

13
Q

What are some laboratory investigations of immunodeficiency?

A
  • FBC
  • test antibody response
  • lymphocyte count
  • neutrophil count
  • test complement function

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