Immunodeficiency

Question 1

What are the clinical features associated with immunodeficiency?

Answer 1

Chronic infection
Recurrent infections (more than expected)
Unusual microbial agents
Incomplete clearing of infection
Incomplete response to treatment

Question 2

What are the types of immunodeficiency?

Answer 2

Primary

Secondary

Question 3

Describe the features of primary immunodeficiency

Answer 3

Mostly genetically determined (from birth)

Involves intrinsic defects in
lymphocytes
complement components
or phagocytic cells

Specific (abnormalities of B or T cells) or non-specific (deficiency in innate components)

Question 4

The type of infection can indicate which part of the immune system is immune deficient.

What deficiencies are Pyogenic infections linked to?

Answer 4

Deficiencies in:
Phagocytosis
Complement
Antibody

Question 5

The type of infection can indicate which part of the immune system is immune deficient.

What deficiencies are opportunistic infections linked to?

Answer 5

Defects in cell-mediated immunity

Question 6

Give examples of pyrogenic infections

Answer 6

Streptococcus pneumoniae
Haemophilus influenzae
Staphylococcus aureus

Question 7

What symptoms are pyrogenic infections linked to?

Answer 7

Pneumonia, sinusitis, otitis media

Question 8

Give examples of opportunistic infections

Answer 8

Gut parasite- Giardia lamblia
Candida albicans
Chickenpox

Question 9

What symptoms are opportunistic infections linked to?

Answer 9

Diarrhoaea, common yeast & viral infections

Question 10

What is the most common inheritance pattern of congenital primary immunodeficiencies?

Answer 10

X-linked

Question 11

Give examples of X-linked congenital primary immunodeficiencies

Answer 11

Chronic Granulomatous Disease (CGD)
Wiskott-Aldrich Syndrome (WAS) 
Severe Combined Immunodeficiency (SCID)
X-Linked Agammaglobinaemia (X-LA)
X-Linked Immunodeficiency with High IgM (HIgM)

Question 12

What can cause congenital primary immunodeficiencies?

Answer 12

The cause of a primary deficiency may vary

Mutations – rare, affect any part of immune system, cause severe disease

Polymorphisms – very common, moderate increased risk of infection

Polygenic disorders- relatively common, affect mainly antibodies, usually cause severe disease

Question 13

Describe the features of polymorphisms for congenital primary immunodeficiencies

Answer 13

Multiple alleles of the same gene occurring at a single locus -in at least 1% of population

Polymorphisms in promoter for TNF – susceptibility to cerebral malaria, septic shock

Chemokines & receptors – susceptibility to HIV

Mannan binding lectin & complement components – susceptibility to fungal and bacterial infections

TLR polymorphisms – susceptibility to various infections

Question 14

Describe the features of polygenic disorders for congenital primary immunodeficiencies

Answer 14

Involves interaction of several genes + environmental factors

CVID, 1 in 20,000 people – mild to severe

IgA, IgG subclass deficiencies - moderate

IgA deficiency, 1 in 700 people - mild

IgG2 deficiency – moderate (pneumococcal, haemophilus infections)