14 - Immunocompromised Host

Question 1

What is an immunocompromised host?

Answer 1

State in which the immune system is unable to respond appropriately and effectively to infectious microorganisms due to a defect in the immune system

Question 2

What causes an immunocompromised state?

Answer 2

Question 3

What are the two types of immunocompromised state and what are the causes?

Answer 3

Secondary could be malnutrition, HIV, chemo, malignancy

Question 4

In general when should you suspect an immunodeficiency?

Answer 4

Severe

Persistent

Unusual

Recurrrent

Question 5

What are some warning signs of PID in adults?

Answer 5

Question 6

What are some warning signs of PID in children?

Answer 6

• 4 or more new ear infections in year
• 2 or more sinus infections or pneumonia in year
• 2 or more months on antibiotics with no effect
• 2 or more deepseated infections
• Family history of PID

Question 7

What are the limitations of the warning signs for PID?

Answer 7

Question 8

What are some primary immunodeficiency diseases of clinical importance?

Answer 8

- Bruton’s disease (X-linked agammaglobulinaemia): defect in B-cell development

- Common variable immunodeficiency (CVID): antibody production defect

- Severe combined immunodeficiency (SCID): combined T and B cell defect so no immunity

- Chronic granulomatous disease: defect in respiratory burst, NADPH oxidase

Question 9

Identify some PID’s due to antibody defects, T cell defects and phagocytic defects.

Answer 9

Question 10

What are the different ages of onset that can help you to distinguish what PID a patient has?

Answer 10

Question 11

When diagnosing a PID, what are some of the factors that can help you narrow down what type it is?

Answer 11

• Age
• Site of infections
• Type of microorganisms and infections
• Family history (X-linked)
• Lab results

Question 12

How do PIDs due to a complement deficiency present?

Answer 12

• Pyogenic infections (C3)
• Meningitis / sepsis / arthritis (C5-C9)
• Angioedema (C1 inhibitor)
• Often infected by neiserria, streptococci, HiB and other encapsulated bacteria, not viruses and fungi

Question 13

How do PIDs due to a phagocytic defects present?

Answer 13

• Skin/mucous infections
• Deep seated infections (abscesses)
• Invasive fungal infection (aspergillosis)

Usually staph aureus, non TB mycohacteria, candida and aspergillus

Question 14

How do PIDs due to an antibody deficiency present?

Answer 14

• Sinorespiratory infections
• Arthropathies
• GI infections
• Malignancies

Mainly strep, staph, HiB, enteroviruses and protozoa giardia lamblia

Question 15

How do PIDs due to T cell defects present?

Answer 15

• Death if not treated
• Failure to thrive
• Deep skin and tissue abscesses
• Opportunistic infection

Similar organisms to antibody deficiency plus salmonella typhii, all viruses and all HIV infections like toxoplasma gondii, cryptococcus neoformans

Question 16

What is Severe Combined Immunodeficiency, Bruton’s disease, CGD and Common Variable Immunodeficiency?

Answer 16

- SCID is a primary immunodeficiency characterised by a severe defect in both the T- & B-lymphocytes

- CVID is a primary immunodeficiency characterised by recurrent infections and low antibody levels (specifically IgG, IgM and IgA)

- Bruton’s disease is an inherited primary immunodeficiency caused by a severe block in B cell development and a reduced immunoglobulin production

- Chronic granulomatous disease is an X-linked inherited primary immunodeficiency wherein the body cannot phagocytose pathogens due to difficulty forming the superoxide radical (no respiratory burst)

• This increases susceptibility to infections by bacteria and fungi

Question 17

What is the diagnosis for the following clinical case?

“A 6 month-old boy was born at term physically normal and apparently healthy. In last 3 months, he has had recurrent fungal (diaper rash, oral candidiasis), viral (upper respiratory tract infections), and bacterial (otitis media) infections, all of which resolved with appropriate pharmacologic intervention

He is below the 50% percentile for weight and has weak IgG response to vaccines. Both sexes of the family have been affected by these infections.”

Answer 17

Severe combined immunodeficiency

Question 18

Answer 18

Bruton’s

Question 19

Answer 19

CGD

Question 20

Answer 20

Common Variable Immunodeficiency (might see Halo signs on CT with pulmonary aspergillosis and skin infections)

Question 21

What is the supportive treatment for PIDs?

Answer 21

Question 22

What is some specific treatment for PIDs?

Answer 22

Question 23

When managing PIDs, what comorbidities should you look out for and how would you prevent comorbities occurring?

Answer 23

• Autoimmunity and malignancies

Question 24

Which conditions is immunoglobulin replacement therapy used for, what is the formulation and what is the goal?

Answer 24

Question 25

Secondary immune deficiencies involve the decreased production of immune component or loss of immune components Provide some causes of this.

Answer 25

- Malnutrition - Infection e.g. HIV - Liver diseases - Lymphoproliferative diseases - Splenectomy

Question 26

In terms of its immune function, explain why the spleen is so important?

Answer 26

Question 27

Patients with a haematological malignancies have increased susceptibility to infections. Why is this?

Answer 27

- Chemotherapy-induced neutropenia - Chemotherapy-induced damage to mucosal barriers (so commensals can get into host) - Vascular catheters (staph aureus)

Question 28

What lab investigations can you look at when narrowing down what deficiency is causing an immunodeficency?

Answer 28