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Flashcards in Hypersensitivity Disorders Deck (96)
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1

Type 1 HD - what is it? mediated by?

Immediate reaction provoked by re-exposure to an allergen.
IgE mediated - Mast cells release mediators resulting in vasodilation, increased permeability, smooth muscle spasm

2

Type 1 HD - Typical Symptoms?

Angioedema, urticaria, rhinoconjunctivitis, wheeze, diarrhoea and vomiting, Anaphylaxis

3

prevalence of allergic disorders in UK in children 13-14 years old

Asthma - 30% (4% also had concurrent clinical food allergy)
Allergic rhinitis - 20%
Atopic dermatitis - 15%
Food allergy - 2.3%

4

What is the atopic triad?

eczema, asthma and hay fever.
Possibly due to hygiene hypothesis

5

T1HD - Atopic Dermatitis (infantile eczema)
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - Irritants, food and environmental
Pathology - Defects in beta defensin predispose to Staph aureus superinfection.
Diagnosis - clinical. 80% present in first year of life
Treatment - Emollients, skin oils, topical steroids, antibiotics, PUVA phototheraphy

6

T1HD - Food Allergy
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - Milk, eggs, peanuts, tree nuts, fish, shellfish
Pathology - IgE (anaphylaxis, OAS); cell mediated (coeliac); IgE/cell mediated (atopic dermatitis)
Diagnosis - Food Diary, skin prick test, RAST, Challenge test. Most resolved by adulthood
Treatment - Dietician, Food avoidance, Epipen, Control asthma if present

7

T1HD - Oral Allergy Syndrome OAS
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - Birch pollen + rosacae fruit, ragweed + melons, mugwort + celery (cross reactivity)
Pathology - exposure to allergen induces allergy to food. Symptoms limited to mouth 2% get anaphylaxis
Diagnosis - Clinically, skin prick testing can be useful
Treatment - Avoid food. If ingested was mouth, take anti-histamine

8

T1HD - Latex food syndrome
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - Chestnut, avocado, banana, patato, tomato, kiwi, papaya, eggplant, mango, wheat, melon
Pathology - Some foods have latex like components and hence latex allergy sufferers will also have food allergies
Diagnosis - Skin Prick Test
Treatment - Strict avoidance of causative food

9

T1HD - Allergic Rhinitis
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - Seasonal (tree and grass pollen, fungal spores), Perennial (pets, house dust mites); Occupational (latex, lab animals)
Pathology - Nasal itch and obstruction, sneezing, anosmia, eye symptoms
Diagnosis - Pale bluish swollen nasal mucosa; Skin Prick Test and RAST
Treatment - Allergen avoidance, Anti-Histamine, Steroid Nasal spray, Sodium Cromoglycate Eye Drops, Oral Steroids, Ipratropium Nasal Spray, Grass pollen desensitisation

10

T1HD - Acute Urticaria
Allergen?
Pathology?
Diagnosis?
Treatment?

Allergen - 50% idiopathic, 50% caused by food, drugs, latex, viral infections and febrile illnesses
Pathology - IgE medicated reaction. Wheals which completely resolve within six weeks
Diagnosis - Mainly clinical (sometimes skin prick test)
Treatment - Allergen avoidance, Anti-Histamines

11

Anaphylaxis

A severe systemic allergic reaction - respiratory diffculty and hypotension
IgE mediated mast cell degranulation - peanut, penicillin, stings, latex
Non- IgE mediated mast cell degranulation - NSAIDs, IV contrast, opiods, exercise

12

Management of Anaphylaxis

Elevate Legs, 100% Oxygen, IM adrenaline 500mcg, inhaled bronchodilators, Hydrocortisone 100mg IV, Chlorphenamine 10mg IV, IV fluids, Seek help

13

Investigations in allergy - Skin prick test
what is it used for? what is a positive test? anything that should be done before the test?

Useful to confirm clinical history. Negative test excludes IgE mediated allergy.
Positive control - histamine, negative control - dilutent
A positive test is a wheal > 2mm greater than the negative control
Discontinue antihistamines 48hrs before test (corticosteroids are ok)

14

Investigations in allergy - Quantitative specific IgE to putative allergen (RAST)
what it does? used for? sensitivity? indications?

Measure levels of IgE in serum against a particular allergen
Confirms dx of allergy and monitors response to anti-IgE treatment
Less sensitive/specific than skin prick testing
Indications - can't stop anti-histamines, anaphylaxis, extensive eczema

15

Investigations in allergy - Component resolved diagnostics

Measures IgE response to a specific allergen protein (whilst conventional tests measure response to range of allergen proteins)

16

Investigations in allergy - Challenge test

Double blind oral food challenge in gold standard for food allergy BUT risk of severe reaction when testing.
Increasing volumes of offending food/drug are ingested under close supervision.

17

Investigations in allergy - During an acute episode

Measure mast cell tryptase (peak at 1-2hrs, baseline by 6hrs)

18

Type II Hypersensitivity Disorders

IgG or IgM antibody reacts with cell or matrix associated self antigen. Results in tissue damage, receptor blockade/ activation

19

T2HD - Heamolytic Disease of the Newborn (HDN)
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen- Antigens on neonatal erythrocytes
Pathology - Maternal IgG mediated retoculocytosis and anaemia
Diagnosis - Positive Direct Coombs Test
Treatment - Maternal Plasma exchange, exchange transfusion

20

T2HD - Autoimmune Haemolytic Anaemia (+ ITP = Evan's Syndrome)
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Numerous autoantigens e.g. Rh blood group Ag
Pathogen - Destruction of RBC by auto antibody + complement + FcR + phagocytes, anaemia
Diagnosis - Positive Direct Coombs Test, Anti Red Cell Ab
Treatment - Steroids

21

T2HD - Autoimmune Thrombocytopenic Purpura
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Glycoprotein IIb/IIIa on platelets
Pathology - Bruising/ Bleeding (purpura)
Diagnosis - Anti platelet Antibody
Treatment - Steroids, IVIG, Anti D antibody, Splenectomy

22

T2HD - Goodpasture's Syndome
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Non- Collagenous domain of basement membrane collagen IV
Pathology - Glomerulonephritis, pulmonary haemorrhage
Diagnosis - Anti GBM Ab, Linear Smooth IF staining of IgG deposits on BM
Treatment - Corticosteroids and Immunosuppression

23

T2HD - Pemphigus vulgaris
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Epidermal Cadherin
Pathology - Non-tense blistering of skin and Bullae
Diagnosis - Direct immunofluoresence showing IgG
Treatment - Corticosteroids and Immunosuppression

24

T2HD - Graves disease
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - TSH receptor
Pathology - Hyperthyroid
Diagnosis - Anti TSH-R Ab
Treatment - Carbimazole and Propylthiouracil

25

T2HD - Myasthenia Gravis
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Acetylcholine receptor
Pathology - Fatiguable muscle weakness, Double Vision
Diagnosis - Anti- ACh-R Ab, abnormal EMG, Tensilion test
Treatment - Neostigmine, Pyridostigmine, (if serious use IVIG and Plasmaphoresis)

26

T2HD - Acute Rheumatic Fever
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - M proteins on Group A strep
Pathology - Myocarditis, Arthritis, Sydenham's Chorea
Diagnosis - Clinical, based on Jones Criteria
Treatment - Aspirin, Steroids and Penicillin

27

T2HD - Pernicious Anaemia
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Intrinsic Factor and Gastric Parietal Cells
Pathology - decreased Hb, decreased B12
Diagnosis - Anti-gastric Parietal Cell Ab, Anti- IF Ab, Schilling Test
Treatment - Dietary B12 or IM B12

28

T2HD - Churg-Strauss Syndrome (eGPA)
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Medium and Small Vessel Vasculitis
Pathology - Allergy -> Asthma -> Systemic Disease (Male predominance)
Diagnosis - p-ANCA (against myeloperoxidase), Granulomas, Eosinophil, Granulomas
Treatment - Prednisolone, Azathioprine, Cyclophosphamide

29

T2HD - Wegener's Granulomatosis (GPA)
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Medium and Small Vessel Vasculitis
Pathology - Sinus Problems, Lung Cavitations + haemorrhage, Cresentic Glomerulonephritis
Diagnosis - cANCA (against Proteinase 3) granulomas
Treatment - Corticosteroids, cyclophosphamide, co-trimoxazole

30

T2HD - Microscopic Polyangitis (MPA)
Antigen?
Pathology?
Diagnosis?
Treatment?

Antigen - Pauci- immune necrotizing, small vessel vasculitis
Pathology - Purpura, lived, many different organs affected
Diagnosis - pANCA (against myeloperoxidase)
Treatment - Prednisolone, Cyclophosphamide or Azathioprine, plasmaphoresis