9.1 Immunocompromised Host

Question 1

Define Immunocompromised host

Answer 1

State in which the immune system is unable to respond appropriately and effectively to infectious microorganism

Question 2

Types of immunodeficiency

Answer 2

Primary immunodeficiency: congenital
Secondary immunodeficiency: acquired

Question 3

Causes for primary immunodeficiency

Answer 3

Intrinsic gene defect
-missing protein
-missing cell
-non-functional components

Question 4

Causes for secondary immunodeficiency CHECK

Answer 4

Underlying disease/treatment

⬇️E.g.) chemotherapy, HIV, malnutrition, splenectomy, haematological malignancies, malnutrition, liver diseases

⬆️protein-sling conditions or burns

Question 5

When should immunodeficiency be suspected

Answer 5

Severe
Persistent
Unusual (site of infection, type of microorganisms causing opportunistic infections e.g. shingles)
Recurrent

Question 6

Examples of defect in antibody production

Answer 6

Common Variable Immunodeficiency
Selective IgA deficiency
IgG subclass deficiency (IgG2)
Hyper-IgM syndrome

Question 7

Clinical condition as a result of defect in B cell development

Answer 7

X-linked agammaglobulinemia (Burton’s disease)
-more common in males than females

Question 8

How is immunodeficiency caused

Answer 8

~65% of PIDs: Antibody defects
-Defect in B cell development
-Defect in antibody production

~15% of PIDs: T cell defects
-Combined B and T cell defects
-T cell defects

~10% of PIDs: Phagocytic defects
-Defects in respiratory burst
-Defect in fusion of lysosome/phagosome
-Defect in neutrophil production & chemotaxis

Question 9

Limitations of the 10 warning signs

Answer 9

Lack of population-based evidence
-family history
-failure to thrive
-diagnosis of sepsis treated with IV antibiotics

PID patients with different defects
-T, B cells/Phagocytes/Complements

PID patients with non-infectious manifestations
-autoimmunity
-malignancy
-inflammatory responses

Question 10

Describe the most common primary immunodeficiency diseases

Answer 10

Common variable immunodeficiency (CVID)
-the patient has B cells but they do not produce any antibodies

Question 11

10 warning signs of PID for adults

Answer 11

・>4 new ear infections within 1 yr
・>2 serious sinus infections within 1yr in the absence of allergy
・1 pneumonia/yr for more than 1yr
・chronic diarrhoea with weight loss
・recurrent, deep abscesses of the skin/internal organs
・persistent thrush for intravenous antibiotics to clear infections
・infection with normally harmless tuberculosis-like bacteria
・family history of PID

Question 12

Clinical conditions related to combined B and T cell defects

Answer 12

Severe combined immunodeficiency (SCID)
Wiskott-Aldrich syndrome
Ataxia telangiectasia

Question 13

Clinical conditions related to T cell defects

Answer 13

Di George syndrome
CD3 deficiency
MHC class II deficiencies
TAP-1/TAP-2 deficiency (MHC class I)

Question 14

Clinical condition of defects in respiratory burst

Answer 14

Chronic granulomatous disease (CGD)

Question 15

Clinical conditions related to defect in fusion of lymphosome/phagosome

Answer 15

Chediak-Higashi syndrome