Immunodeficiency

Question 1

Definition of immunodeficiency

Answer 1

Clinical situations where the immune system is not effective enough to protect the body against infection

Question 2

Definition of primary immunodeficiency

Answer 2

Inherent defect within the immune system - usually genetic

Question 3

Definition of secondary immunodeficiency

Answer 3

Immune system affected due to external causes

Question 4

Secondary causes of immunodeficiency

Answer 4

Breakdown in physical barriers (e.g. cystic fibrosis)
Protein loss (e.g. burns, protein losing enteropathy, malnutrition)
Malignancy (e.g. lymphoproliferative disease, myeloma)
Drugs (e.g. steroids, DMARDS, rituximab, anti-convulsants, myelosuppressants)
Infection (e.g. HIV, TB)

Question 5

Pathogen Recognition Receptors

Answer 5

Recognise conserved pathogen associated molecular patterns (PAMPs) which are unique to each pathogen (e.g. Lipopolysaccharides)

Question 6

IRAK4 deficiency

Answer 6

Presents with recurrent bacterial infection (especially streptococcus and staphylococcus) e.g. pneumonia, meningitis, arthritis
Poor inflammatory response
Susceptibility to infection decreases with age
Prophylactic antibiotics, IV immunoglobulins if severe
MyD88 presents in a similar manner

Question 7

Chronic granulomatous disease

Answer 7

NAPDH complex on phagocytes non-functional, forming granulomas
Recurrent abscesses in lung, liver, bone, skin and gut
Unusual organism e.g. Staphylococcus, Klebsiella, Serretia, Aspergillus, Fungi
Rx: haemopoietic stem cell transplant, antibiotics

Question 8

Complement deficiency (C2, C4)

Answer 8

SLE, infections, myositis

Question 9

Complement deficiency (C5-C9)

Answer 9

These form the membrane attack complex

Presents with repeated episodes of bacterial meningitis (particularly Neisseria meningitis)

Question 10

X-linked agammaglobulinaemia

Answer 10

Primary antibody deficiency
Male, young presentation
Recurrent infections, especially respiratory
Family history likely
Lack of immunoglobulins and B cells

Question 11

CVID

Answer 11

Common Variable Immune Deficiency

Question 12

Antibody deficiency treatment

Answer 12

Antibiotics

IgG replacement

Question 13

SCID

Answer 13

Severe Combined Immunodeficiency
Diagnosis made by lack of T cells and suggestive history
Rx: Paediatric emergency, antibiotics/antivirals/antifungals, asepsis, haemopoietic stem cell transplant (only cure)
Caused by defect/absence of critical T cell molecule, loss of communication (MHCII deficiency), or metabolic (e.g. adenosine deaminase deficiency)