Infection In The Immunocompromised

Question 1

When and why do severe cases of primary immunodeficiency disorders present

Answer 1

In the first year after birth

1. Immune system not needed in utero
2. Maternal antibody + lactation protect for first few months

Note: 60% of ppts are male - X-linked genes commonly implicated

Question 2

Describe 3 ways to manage primary immunodeficiency disorders

Answer 2

1. Passive immunisation (in primary antibody deficiency) with IgG pooled from healthy blood donors
2. Haematopoietic stem cell transplant
3. Gene therapy (*trials) purify own blood sample and insert correct gene into genome of stem cells

Question 3

Outline 6 causes of acquired immunodeficiency

Answer 3

1. HIV
2. Malnutrition - vicious cycle (3) alcoholics
3. Old age - reduced response to vaccine, t cell function, antibody response, memory cells limited to fewer pathogens (CMV)
4. Iatrogenic - Glucocorticoids, immunosuppressants, cytotoxic drugs
5. Other diseases - cancer, TB, DM
6. Hyposplenism - surgical removal, sickle cell disease, risk of sepsis from circulating encapsulated bacteria

Question 4

Describe 3 general features of immunodeficiency disorders

Answer 4

1. Increased risk of infection - more severe conventional and opportunistic
2. Increased risk of certain cancers - immunocompromised host with persistent oncogenic viral infection = more mutations = malignancy
3. Increased risk of autoimmune disorders - e.g. loss of Treg cells = autoimmunity

Question 5

Define opportunistic infection

Answer 5

1. Infections which don’t cause symptomatic disease with normal immune system
2. Pattern of infection/malignancy are seen in proportion to the precise nature and extent of immune dysfunction

Question 6

Explain the common presentations of undiagnosed HIV in countries with and w/o TB

Answer 6

High TB prevalence “see TB think HIV, vice versa” at any CD4 count

Low TB prevalence - pneumocystis pneumonia at low CD4 cell count per microlitre

Question 7

Describe (5) common dermatologic manifestations in undiagnosed HIV patients

Answer 7

1. Rash on palms and soles - HIV seroconversion illness
2. Staphylcoccal infection - persistent folliculitis, superficial abscesses
3. Fungal infection - onychomycosis, tinea increased severity
4. Herpes zoster (shingles)
5. Herpes simplex (cold sores)

Question 8

Name (4) oral and (5) genital mucosal lesions associated with immunocompromised hosts

Answer 8

Oral:

1. Hairy leukoplakia
2. Candidiasis (thrush)
3. Ulceration
4. Kaposis sarcoma

Genital:

1. Candidiasis
2. Herpes simplex
3. Cervical dysplasia
4. Carcinoma in situ (anal/cervical)
5. Perianal ulceration

Question 9

Describe the most common bacterial vs fungal pneumonia presentations in undiagnosed HIV

Answer 9

Bacterial: pneumococcus - presents at any stage of HIV, more likely <500 CD4. Lobar pneumonia, meningitis, sinusitis

Fungal: Pneumocystis jiroveci - most common AIDS-defining illness in high income countries. Gradual over weeks - fever, dry cough, SOB, desaturation with exercise

Question 10

Name a common fungal pathogen responsible for meningitis in the immunocompromised

Answer 10

Cryptococcus neoformans

Question 11

Identify malignancies that may arise from the following oncogenic viruses

1. EBV
2. HHV8
3. HPV (type 16, 18)

Answer 11

EBV - lymphomas (Hodgkin and non-hodgkin, primary CNS)

HHV8 (human herpesvirus 8) - kaposi sarcoma, primary effusion lymphoma

HPV (human papillomavirus) squamous carcinoma cervix and anus