Hypersensitivity reactions

Neelika Malavige

Objectives

• Describe the diseases association with type I hypersensitivity reactions (allergies)

• Discuss the pathogenesis of these diseases

• List the diagnostic tests available to evaluate a patient with allergies

• Briefly describe the principals of management of patients with allergies

Case study 1:

Presentation: • Samanmali, 6 year old girl is brought to the casualty

with difficulty in breathing and a cough for 2 days duration.

• 6th visit to the ETU within 1 year. • Has had wheezing episodes on most days during the

past year and has missed school on a number of occasions. Current episode is triggered by a URTI.

Examination:• Dyspnoeic. Respiratory rate 40• intercostal and suprasternal recessions+• Rhonchi++.

Current treatment: • beclamethasone inhaler (200mg bd) and a salbutamol

inhaler (bd).• Inhalation technique is satisfactory.

Past medical history: • atopic dermatitis when she was 1 year old . The rash

gradually got better when she was 4 years old.

Family history: • 8 year old brother has bronchial asthma. • Father has allergic rhinitis.

a) Bronchial asthma

b) COPD

c) Allergic rhinitis

d) Chronic urticaria

e) Atopic dermatitis

f) Papular urticaria

Which of the following are mediated by type 1

hypersensitivity reactions (atopic diseases)?

Atopic diseases: the clinical spectrum

• Bronchial asthma (allergic)

• Atopic ezcema/dermatitis

• Allergic rhinitis

• Food allergies

a) Eosinophils

b) Neutrophils

c) CD8+ T cells

d) TH2 subset of CD4+ T cells

e) Natural killer cells

Q: Which of the following cells play a role in

the pathogenesis of allergic bronchial

asthma?

1. Aeroallergen specific skin prick tests

2. Aeroallergen specific IgE detection in serum

3. Lung function tests

4. Bronchoalveolar lavage

5. Sputum culture

6. Lung biopsy

7. High resolution CT scan

Q: What investigations would help is to find out

the cause of repeated asthmatic attacks in this

patient?

What types of tests are available for diagnosis of allergy?

• Skin prick tests

• In vitro tests: measuring allergen specific IgElevels

Patch testing is for diagnosing allergens causing contact

dermatitis. This is not a test for diagnosis of IgE mediated

allergic reactions.

Skin prick tests

The suspected allergen is

injected by a sterile

lancet intradermally.

The diameter of the

reaction is recorded after

20 minutes.

Very rarely skin prick tests can cause anaphylaxis. Should

be done by trained individuals!!!

Common allergens that are responsible for asthma

House dust mite Cockroaches moulds

Cats (pets) Pollen

Indoor aeroallergen sensitization in asthma and AR patients in SL

• House dust mite: 82%

• Indoor moulds: 32%

• Cockroach: 46%

All 3 allergens: 10%

HDM and cockroach: 32%

We found that this patient was sensitized to house dust

mite. What next?

Immunotherapy

Case study 2:

A 30 year old patient is referred from the CSTH with several episodes of anaphylaxis. He has had 4 episodes of anaphylaxis during the year 2011. His referral letter states that the cause of anaphylaxis cannot be identified.

Careful history indicates all episodes occurred following ingestion of sesame seeds or sesame oil.

1. Itching of the tongue while eating

2. Rapid progression of symptoms

3. Abdominal pain

4. Difficulty in breathing

5. Feeling faint

Q: What are the clues in the history that suggest

that he is likely to be having an allergic reaction

to food?

Q: How would you determine the cause of anaphylaxis in this patient?

1. Skin prick testing using suspected allergens

2. Determining allergen specific IgE antibodies

3. Patch testing

4. Testing with possible types of food to determine which one he is allergic to

Serum IgE levels were measured by the immunocap

method.

Very high sesame seed IgE levels were detected.

What next? What if he gets another episode of anaphylaxis.

Interpretation of allergy tests

• Always correlate with clinical history. Presence of allergen specific IgE antibodies in the absence of clinical allergy can occur!!!

• So be cautious when interpreting reports.

Important!!!! You will NOT be tested on this.

What allergies can be tested with skin prick tests?

• Majority of food allergens

• Inhalant allergens

• Some occupational allergens: latex

What can be tested by blood tests for specific IgE

• Food allergens: wider range

• Inhalant allergens

• Occupational allergens: latex, isocyanates, percholates, anhydrides

• Insect venom allergy: bees, wasps, ants

Case 3:

A 42 year old male presents with swelling of the eyes,

tongue and difficulty in breathing. This is the 3rd episode in

a period of 2 months. Occurs around 12 in the night.

Patient cannot figure out any food allergy.

P/M/H: Known hypertensive. Has been on captopril and

lovastatin for the past 2 years.

Family history: father had died of IHD at 65 years of age.

What is Angio-oedema?

• Angio-oedema consists of transient swellings of deep dermal, subcutaneous and submucosal tissues

What are the causes of angio-oedema?

• Allergies

• Autoinflammatory diseases

• Hereditary or acquired C1 esterase inhibitor deficiency

• Drugs: ACE inhibitors, NSAIDS, Opiates, antibiotics

• Idiopathic: chronic urticaria and angio-oedema

A 25 year old female complains of a itchy rash all over

her body. She says its worse towards to evenings and

raised bumps occur all over the body., especially behind

ears and the neck area. She has had it for 3 months now

and it occurs on most days of the week.

What is the likely cause of her chronic urticaria?

a) A food allergy

b) Allergy to ‘heaty’ food

c) Insect bite allergy

d) Autoimmune urticaria

e) Cholinergic urticaria

What is the pathogenesis of this condition?

a) Type I hypersensitivity

b) Type II hypersensitivity

c) Type III hypersensitivity

d) Occurrence of IgG antibodies to IgE antibody

e) Post viral

Occurs due to IgG or IgM antibodies against IgE antibodies.

Can be assessed by ASST or Basophil activation test

(basophil activation markers of CD63 and CD203c)

Summary

• Allergy (type I hypersensitivity reactions) are responsible for many diseases.

• Most of them are chronic (asthma, allergic rhinitis, atopic dermatitis).

• Sometimes it can cause life threatening reactions.