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Flashcards in Clinical conditions Deck (42)
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1
Q

What immunologic phenomenon leads to toxic shock syndrome?

A

binding of bacterial superantigens, outside the MHC grove leading to massive activation of T-cells, cytokine release

2
Q

What infections does a lack of neutrophils/monocytes cause?

A

High grade bacterial infections - Staph aureus, gram negative bacteria (E.coli, proteus, serratia, pseudomonas)
Invasive fungal infections (aspergillus, candida)

3
Q

What infections does lack of T-cells result in?

A
Fungi (typically mucosal candida)
Mycobacteria
Viruses (CMV, VZV, HSV, Protozoa)
Protozoa (pneumocystits)
Listeria
4
Q

What infections does lack of antibody response result in?

A

Recurrent sinopulmonary and gut infections
Infections by
- polysaccharide encaspulated organisims (Strep pneumoniae, H.influenzae, Strep pyogenes, Branhamella)
- staph aureus
- Giardia
- campylobacter

5
Q

What does a lack of early complement components (C1, C2, C3) lead to?

A

Autoimmune disease, such as SLE, vasculitis, GN

6
Q

What does a lack of later complement products lead to?

A

Infection with Neisseria - often disseminated

7
Q

Why is nephrotic syndrome an immunosuppressed state?

A

Loss of IgG with loss of albumin

8
Q

What is the most common cause of a low CH50 (total haemolytic complement)?

A

Delay in specimen transport to lab

9
Q

What are the lab findings in CVID (common variable immunodeficiency)?

A

Low IgG (and one or both of low IgA and IgM)
B cell count normal in most
Electrophoresis - hypogamma
Impaired vaccination response as no memory B cells

10
Q

What is the treatment for CVID?

A

IV immunoglobulin - every month due to the half life of IgG
Antibiotics for infections
Avoid live vaccines

11
Q

What are some clinical manifestations of CVID?

A

Recurrent sinopulmonary infections
Gastrointestinal infections
Skin infections
Autoimmunity (immune cytopenias, thyroid, pernicious anaemia, polyarthropathy, polymyositis, vitiligo)
Increased risk of cancer - lymphoma, gastric cancer
Allergic disease, chronic infections, amyloid

12
Q

What is Brutons syndrome?

A

X-linked agammaglobulinemia with no B-cells and no immunoglobulin production
Absence of Brutons tyrosine kinase which is a signalling molecule that matures B-cells

13
Q

What are some conditions associated with IgA deficiency?

A
Atopic disease
Cows milk allergy
Coeliac disease
Inflammatory bowel disase
RA, SLE, dermatomyositis, sjogrens
ITP, Pernicious anaemia, thyroiditis, addisons
Anaphylaxis to blood transfusion
14
Q

Treatment for IgA deficiency?

A

No role for IvIg
Prompt antibiotics
Transfusions from IgA deficient donors or washed

15
Q

What is Hyper IgM syndrome?

A

X-linked CD40 ligand deficiency = absence of T and B-cell communication = failure of B-cell isotype switching and memory B cell generation
Features similar but more severe then CVID and addition of T-cell related infections ie. PCP

16
Q

Lab findings in Hyper IgM syndrome?

A
Low IgA, IgG, IgE but normal or increased IgM (as not able to class switch)
Normal circulating B cells (but only express IgM and IgD = naive B cell markers)
Flow cytometry positive for CD40L
17
Q

What is chronic granulomatous disease?

A

Deficiency in the NADPH oxidase leading to inability to create oxidative burst inside the neutrophil and kill the organism - therefore neutrophils engulf pathogens but are unable to kill them (granuloma formation)

18
Q

Clinical features of chronic granulomatous disease?

A
Recurrent infections of skin/lungs with coagulase negative bacteria/fungi
Staph infections of skin
Purulent dermatitis
Broncopneumonia
Chrons like syndrome
19
Q

Test for chronic granulomatous disease?

A

Ability of granuloctyes to generate an oxidative burst

= NBT test (nitroblue tetrazolium test) induces oxidative response in normal neutrophils

20
Q

What is a type 1 hypersensitivity reaction?

A

Immediate
IgE mediated
Urticaria, angioedema, anaphylaxis, asthma, rhinitis, conjunctivitis

21
Q

What is a type 2 hypersensitivity reaction and examples?

A

Cytotoxic
Antibody directed against antigen on cells or cell membrane and result in activation of complement via the classic pathway
Examples: Transfusion reactions, autoimmune haemolytic anaemia, good pastures syndrome

22
Q

What is a type 3 hypersensitivity reaction and examples?

A

Immune complex mediated
Antibody-antigen complexes are circulating and become trapped in a cell component and activate complement via the alternate pathway
Examples: Glomerulonephritis, serum sickness, vasculitits

23
Q

What is a type 4 hypersensitivity reaction and examples?

A

Delayed hypersensitivity
T-cell mediated
Takes 2-3 days to develop
Inappropriate or excessive immune response by CD4 subsets (TH1 and TH17)
Examples: contact dermatitis, SJS, TEN, DRESS, delayed urticaria

24
Q

Investigations in allergic rhinitis?

A
Skin prick testing 
Specific IgE (RAST test) - less favoured, radioimmunoassay that detects specific IgE to known allergens
25
Q

Management of allergic rhinitis?

A
Avoid allergen
Intra-nasal corticosteroids
Anti-histamines
Decongestants
Can do desensitisation in severe disease
26
Q

What are some contrindications to skin prick testing?

A
Antihistamines (false negatives)
TCAs
Topical steroids
Severe eczema
Dermatographism
27
Q

What is the cellular change behind desensitisation/immunotherapy?

A

Down regulation of the TH2 response and up-regulation of the TH1 response

28
Q

What are the common foods causing allergies?

A
Cows milk
Egg
Wheat
Soy
Seafood
Nuts
29
Q

What food allergies are you less likely to grow out of?

A

Seafood

Nuts (peanut)

30
Q

Investigation of food allergy?

A

Skin prick testing
Specific IgE (RAST)
Oral food challenge (gold standard but only used if above is abnormal)

31
Q

Management of food allergy?

A

High risk allergen - e.g. peanut and asthma = give epipen
Avoid certain foods
Watch for cross-reactivity e.g latex and avocado/kiwfruit
Immunotherapy under trial

32
Q

What is the peak time for tryptase?

A

peaks in 60-90 minutes, last 5 hours

33
Q

What is hereditary angioedema?

A

Mutation in SERPING1 gene which codes for C1 inhibitor protein
- leads to deficiency or loss of function of C1 inhibitor with increased production of bradykinnin down kallkrenin pathway

34
Q

What are the 3 types of HAE?

A

Type 1 - low levels of C1INH
Type 2 - dysfunctional C1INH but normal levels
Type 3 - mutation in gene encoding factor XII which has a role in bradykinin synthesis

35
Q

Tests in Type 1 HAE

A

low C4
low C1-INH both level and function
*must be less than 50% on 2 occasions
normal C1q (determines it from aquired AE)

36
Q

Tests in Type 2 HAE

A

low C4
normal or high C1-INH levels but low function, less than 50% on 2 occasions
normal C1q

37
Q

Inheritance of HAE?

A

Autosomal dominant

38
Q

Age of onset of HAE?

A

Less than 40 years

- typically less than 20 years of age

39
Q

Presentation of HAE?

A

Angiodema without urticaria or puritis
Triggers - physical/emotional stress, drugs, oestrogen
gradual onset of either
- gut odema = abdo pain, vomitting, diarrhoea
- skin = face, lips, limb swelling
- upper airways = larnyneal odema

40
Q

Treatment of HAE?

A

Doesn’t respond to steroids, anti histamines, adrenaline

Treatment

  • C1 INH plasma concentrate from pooled plasma
  • Bradykinin-2-receptor antagonist e.g Icadibant
  • Ecallantide (only available in USA, kalikrenin inhibitor)
  • if above unavailable can give FFP
41
Q

What is acquired angiodema?

A

similar to HAE but not hereditary, develops in older people, over the age of 40
due to lymphoproliferative disorders or autoimmune disease

42
Q

Tests in AAE?

A
low C4
low C1q (different from HAE)
low or normal C1 inhibitor level with low C1 inhibitor function