S9: the immunocompromised host

Question 1

What is an immunocompromised state? When would you suspect immunodeficiency?

Answer 1

Immune system is unable to respond appropriately & effectively to infectious microbes
-can be due to defect in one or more components of the immune system
SPUR – severe, persistent, unusual & recurrent

Question 2

List the different types of primary immunodeficiency disease

Answer 2

Antibody defects
-defect in B cell development: X-linked agammaglobulinaemia (Bruton’s disease)
-defect in antibody production: common variable immunodeficiency (requires treatment), selective IgA deficiency (does not require treatment & most patients are asymptomatic)
T cell defects
-combined B & T cell defects: severe combined immunodeficiency
-T cell defects: Di George syndrome
Phagocytic defect
-defects in respiratory burst: chronic granulomatous disease

Question 3

What is the difference between primary and secondary immunodeficiency?

Answer 3

Primary = congenital -> due to intrinsic gene defect 
Secondary = acquired -> due to underlying disease/treatment

Question 4

What is the likely primary immunodeficiency to be based on age of onset?

Answer 4

Onset < 6 months old = T cell or phagocyte defect
6 months < onset < 5 years = B-cell, antibody or phagocytic defect
Onset > 5 years = B-cell/antibody/complement or secondary immunodeficiency

Question 5

What causes secondary immunodeficiency?

Answer 5

Result of decreased production of immune components
Causes: malnutrition, infections, liver diseases, lymphoproliferative diseases or asplenism
Note: asplenic patients need to be especially careful -> given life-long penicillin prophylaxis & immunisation against encapsulated bacteria
-NHS: Neisseria menigitidis, haemophilus influenza & strep pneumoniae

Question 6

How are primary immunodeficiencies managed?

Answer 6

Supportive treatment = prophylactic antibiotics, passive immunisation, nutritional support (vitamin A & D)
Specific treatment – regular immunoglobulin therapy, haematopoietic stem cell therapy
Treat comorbidities – assess organ damage, autoimmune & malignancy treatment if disease arises

Question 7

Describe aspergillus infection in the immunocompromised

Answer 7

Genus of conidial fungi
Aspergillus fumigatus is the most common organism causing aspergillosis
-primarily colonises paranasal sinuses & lungs -> necrotising pneumonia
-diagnosis of pulmonary aspergillosis: characteristic ‘halo’ signs in HRCT (high resolution CT) scans

Question 8

Describe VZV infection in the immunocompromised

Answer 8

Varicella zoster virus (VZV)/shingles is a common infection in immunocompromised patients
Primary infection (chickenpox) = usually disseminated & remains latent by establishing itseld in multiple sensory dorsal root ganglia
Secondary infection = reactivation of virus occurs & commonly presents as shingles
-painful rash of papules (blisters) with erythema that usually follow dermatomal patterns
-treatment with pain relief & aciclovir