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ESA 3 > Infection 10 (Not Finished) > Flashcards

Infection 10 (Not Finished) Flashcards

1
Q

Why are immunodeficiencies important to recognise in clinical practice?

A

Associated with:

Increased frequency and severity of infections

Autoimmune disease and malignancy

Failure to recognise leads to increased morbidity and mortality

37% of immunodeficient patients will have permanent tissue/organ damage

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2
Q

Define ‘Immunocompromised host’

A

State in which the immune system quantitatively or qualitatively defective and hence is unable to respond appropriately and effectively to infectious micro-organisms

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3
Q

What key components of the immune system are commonoly affected by immune deficiency?

A

Innate:

Innate barriers

Phagocytes

Complement

Adaptive:

B Cells

Antibodies

T Cells

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4
Q

What features of infections may suggest an underlying immune deficiency?

A

SPURS:

Severe

Persistent

Unusual (microbe or site)

Reccurent

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5
Q

What organisms or infection sites might be suggestive of immune deficiency?

A

Organisms:

Natural commensals

Sites:

Deep skin/organ infections (often ulceration present)

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6
Q

Contrast Primary and Secondary Immunodeficiency (ID)

A

Primary:

Intrinsic defect

E.g. Single gene disorders, polygenic disorders or defective HLA polymorphisms

Secondary:

Underlying disease affection immune components

Either lack of production of immune factors or increased loss or catabolism

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7
Q

How do we classify Primary IDs?

A

Classified by which immune component is affected:

B Cell (50%)

T Cell (30%)

Phagocytes (18%)

Complement (2%)

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8
Q

What is the prevalence of Primary IDs?

How are patients distributed across age and gender?

A

1:400 to 1:400,000 depending on disease

80% of Patients <20yrs at onset:

Often onset is in first few months of life

70% Male:

Often X-Linked defects

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9
Q

What are the 10 major warning signs for Primary IDs?

A

4+ new ear infection/yr

2+ new serious sinus infections/yr

2+ months of antibiotic treatment with little effect

2+ pneumonias/yr

Failure to thrive

Reccurent deep skin/organ abscesses

Persistent buccal thrush or fungal skin infections

Need for IV antibiotics to clear infections

2+ deep seated infections (incl. septicaemia)

Family history of PID

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10
Q

Give 2 B Cell deficiencies

For each give the defect, when they present and important serological findings

A

Common variable immunodeficiency (CVID):

Inability of B cells to mature to plasma cells

Can present at any stage of life

IgG < 5g/l

IgA/M variable

Bruton’s Disease (X-Linked agammaglobulinaemia):

Impaired B cell development

Generally presents in first year of life

IgA < 2g/l

IgA undetectable

Low B cells

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11
Q

How might a patient with Primary ID present?

A

Any of the below:

With reccurent upper and lower resp infections (bacterial infections can lead to bronchiectasis)

With GI complications including infections (Giardia)

With an Arthropathy (Mycoplasma/Ureaplasma spp.)

With an Autoimmune disease (increased incidence)

With lymphoma or gastric carcinoma (+50% risk with CVID)

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12
Q

How might a patient with Primary ID be managed?

A

Primary:

Prompt/prophylactic antibiotics

Ig replacement therapy

Accessory:

Management of resp function

Avoidance of radiation exposure (reduce cancer risk)

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13
Q

Describe a typical presentation of a patient with CVID

A

Any age

Reccurent bacterial infections (Esp. URTI/LRTI)

May be associated with autoimmune disease

Some have granulomatous disease

Generally no family history of CVID

Low IgG

Variable IgA/IgM (Normally low, pan-hypogammaglobulinaemia)

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14
Q

What is the goal of effective Ig replacement therapy (IRT)?

What conditions is it useful for?

How long is a treatment course of IRT?

A

Serum IgG <8g/l

Conditions:

CVID

XLA (Bruton’s)

Hyper-IgM syndrome

Treatment length:

Lifelong

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15
Q

Give 3 examples of important primary phagocyte deficiencies, give the defect seen in each

A

Leukocyte adhesion deficiency:

Lack of CD18 protein on phagocytes that prevent adhesion to epithelium

Chronic granulomatous disease (GCD):

Difficulty forming ROS impairing oxidative burst and intracellular killing of ingested pathogens

Chediak-Higashi Syndrome:

Failure of phagolysosome formation leading to a lack of effective phagocytosis

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16
Q

How might a patient with primary phagocyte deficiency present?

A

Prolonged reccurent infections, for example:

Catalase +ve staphyloccocal infection:

  • Skin and mucous membrane ulcers*
  • Osteomyelitis*
  • Deep abscesses*

Invasive aspergillosis

Inflammatory problems (granuloma formation)

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17
Q

How might a patient with primary phagocyte deficiency be managed?

A

Prophylactic antibiotics/anti-fungals/immunisation

Surgical mangement

Interferon-G (CGD specific)

Steroids (CGD specific)

Stem cell transplantation (Potential cure)

18
Q

Describe the presentation of a patient with CGD

A

Pulmonary aspergillosis

Skin infections where scarring occurs at infection site

19
Q

List 2 important primary T cell deficiencies and briefly state their cause

A

Di George syndrome:

Lack of thymus (defect in embryogenesis)

Severe combined immunodeficiency (SCID):

Stem cell defect

Or

Death of developing thymocytes (haemopoietic progenitor cells that develop into T cells)

20
Q

Describe the common features of Di George Syndrome

What is the prevalence?

A

CATCH-22:

Cardiac abnormalities

Abnormal facial features

Thymic hypoplasia

Cleft palate

Hypocalcaemia

22 is the chromosome abnormality

Prevalence:

1:4000 live births

21
Q

How might someone with DiGeorge syndrome be managed?

A

Neonatal cardiac surgery

Supplements to correct hypocalcaemia

Depending on immune defect:

If <0.4x10^9/l T cells then pneumocystis pneumonia prophylaxis (antibiotics)

Severe forms requires bone marrow transplant

No Live vaccines (BCG, MMR, Oral Polio)

22
Q

How might a patient with SCID present?

A

Failure to thrive (seen in young children)

Long term antibiotic therapy patient

Deep skin/organ abscesses

Low lymphocyte count (<4.0 - 10.0/ul)

High susceptibility to all infections, particularly fungal and viral infection:

  • Pneumocystis pneumonia*
  • Varicella zoster virus*
  • CMVs*
  • Epstein Barr virus*
23
Q

Describe the management of a patient with SCID

A

Short term:

No Live vaccines

Only irradiated CMV- blood products

Aggressive infection treatment

Prophylactic antibiotics/antifungals

IV Ig Therapy

Long term:

Bone marrow transplant/Stem cell transplant

Gene therapy

24
Q

What are the possible categories of dysfunction seen in patients with complement component deficiencies?

For each, give the complement component(s) that might be deficient

A

Immune complex disease:

C1

C2

C4

Reccurent bacterial infections:

C3

Reccurent nesserial infections

C5-9

D, B, P

25
Q

In regard to secondary immune deficiencies, what are some of the causes of lowered production of immune components?

A

Malnutrition

Infection (E.g. HIV)

Liver disease

Lymphoproliferative disease

Drug induced Neutropenia

Splenectomy patients

26
Q

What are some of the causes for a patient needing a splenectomy/being asplenic?

A

INfarction (E.g. Sickle cell disease)

Trauma

Autoimmune haemolytic disease

Infiltration (E.g. Tumour)

Coeliac disease

Congential

27
Q

Define ‘neutropenia’

A

Neutrophil deficiency

28
Q

What factors might cause neutropenia?

A

Bone marrow inflitration w/cancer

Chemotherapy (esp. cytotoxic or immunosuppressant)

Alcohol abuse/Other drugs (E.g. Phenytoin)

Infection (E.g. Hep B/C, HIV, CMV)

Opportunistic infection

Autoimmune

Aplastic anaemia

Radiotherapy

29
Q

How might a patient with a neutrophil count of <1.0x10^9/l be managed?

A

If suspected neutropenic sepsis:

Treat with empiric antibiotics immediately

Then assess risk of septic complications, treat complications

30
Q

How might an asplenic patient that is acutely unwell present?

A

With an OPSI (overwhelming post-splenectomy infection):

H. influenzae

S. pneumonae

N. Meningitidis

Sepsis/Meningitis common

31
Q

How is a post-splenectomy/asplenic patient managed?

A

Penicillin prophylaxis

Immunisation against encapsulated bacteria (2 weeks before splenectomy if possible)

Medic alert bracelet (I am asplenic)

32
Q

What are the important immune functions of the spleen?

A

IgM (short term) and IgG (long term) production

Reserve of monocytes (50% of total in body)

33
Q

Why are asplenic patients particularly suseptible to infection by encapsulated bacteria?

A

Antibodies produced in the white pulp of the spleen are critical for phagocytosis of encapsulated bacteria

Complement system is able to compensate with unencapsulted bacteria as it can opsonise these microbes

However, the complement system is unable to to opsonise encapsulate bacteria

34
Q

In regards to secondary IDs, what might be the cause of increased loss or catabolism of immune components?

A

Protein loss conditions:

Nephropathy

Enteropathy

Burns

35
Q

Outline the lab tests of humoral immunity

A

IgG, IgA, IgM (+/- IgE) counts

IgG1-4 Subclass count

IgG levels to specific previous vaccines (E.g. Tetanus, MMR):

Antibody response to micro-organisms elicited to test immunisation

36
Q

Outline the lab tests for cell mediated immunity

A

Lymphocyte count (FBC)

Lymphocyte subset analysis (CD4+, CD8+, T, NK, B cells)

In vitro tests of T cell function

37
Q

Outline the lab tests for phagocytic cells

A

Neutrophil count (FBC)

Neutrophil function tests (E.g. Test oxidative burst for CGD)

Adhesion molecule expression test (For LAD)

38
Q

Outline the lab tests for the complement system

A

Individual component count

Tests of individual complement function

39
Q

How can a patient be definitively tested for Primary ID?

A

Molecular testing and genetic screening

40
Q
A

ESA 3 (54 decks)

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