Infection in the Immunocompromised Host

Question 1

Name some examples of diseases which cause a deficiency in the immune system

Answer 1

• G6PD defieincy,
• DiGeroges syndrome
• AIDS,
• X-linked agammaglobinamia
• Hyposplenism

Question 2

What are the different defences to infection?

Answer 2

• Anatomical barriers,
• Innate immunity - complement, neutrophils, macrophages and NK cells
• Adaptive immunity - T (CD4 and CD8) and B cells

Question 3

What are some immunosupressive agents?

Answer 3

• Glucocorticoids (inhibition of cytokine production, suppressing antigen presentation, suppressing INF gamma)
• Chemotherapy (suppressing production of T and B cells, Mucositis disrupts anatomic barrier)
• Immunosuprressant eg, methotrexate, leflunomide, monoclonal antibodies

Question 4

What are some examples of antibody disorders?

Answer 4

• X linked agammaglobinemia
• Selective IgA deficiency (most common) - infections on mucosal surface eg, recurrent sinus infections and blood transfusion reactions

Question 5

What are some disorders of Neutrophils?

Answer 5

• Chronic granulomatous disease (lack of NADPH) especially at risk of pulmonary infections eg, aspergillus,
• Leukocyte adhesion deficiency

Question 6

What are some T cell disorders?

Answer 6

• DiGeorge’s syndrome - congenital heart disease, learning difficulties, hypocalaemia, recurrent viral/fungal disease

Question 7

What are some combined B and T cell disorders?

Answer 7

• Severe combined immunodeficiency
• Ataxic telangiectasia

Question 8

What antibiotics are given to the standard risk neutropenic/immunocompromised adults?

Answer 8

• Tazcin and vancomycin

Question 9

What is the antibiotic treatment for critical risk neutropenic/immunocompromised patients?

Answer 9

IV meropenem and IV amikacin and IV vancomycin.
May need to add additional antimicrobials depending on what pathogen you suspect/any resistance/ MRSA status

Question 10

What are some examples of opportunistic microorganisms

Answer 10

• Candida albicans,
• Staphylococcus aureus,
• Pseudomonas aeruginosa,
• H. influenza,
• Strep. pyogens,
• Neisseria meningitidis,
• Aspergillosis,
• Cryptococcus,
• CMV,
• VZV,
• HSV

Question 11

What are some infections seen in transplant patients?

Answer 11

• Mycobacteria,
• Cryptococcus neoformans
• CMV

Question 12

What are primary and secondary immunodeficiency syndromes?

Answer 12

• Primary = genetic causes
• Secondary = AIDS, relating to underlying disease (cushing’s or burns etc) or related to therapeutic immunosuppression

Question 13

Hyposplenism increases your risk of what?

Answer 13

Encapsulated bacteria such as strep. pneumoniae, haemophilus influenzae and Neisseria meningitidis. Given penicillin V prophylaxis

Question 14

What are the blood film features of hyposplenism?

Answer 14

Howell-jolly bodies and siderocytes