Allergy and Immunology

Question 1

What are 4 differentials for a pediatric itch?

Answer 1

1) Bites (eg. scabies, lice, mosquito bites)

2) Dermatitis (eg. atopic/contact derm)

3) Urticaria

Question 2

What are 8 differentials for rash ±fever in a child?

Answer 2

1) Cows milk protein allergy
2) Dengue
3) Dermatitis
4) Drug rxn
5) Immune thrombocytopenia purpura
6) Infectious mononucleosis syndrome
7) Other inflammatory conditions (eg. HSP, Kawasaki, JIA)
8) Fungal infection (tinea)
9) Bacterial infection (impetigo, cellulitis)
10) SLE
11) Urticaria
12) Viral exanthem and enanthem

Question 3

What are 5 kinds of allergic reactions?

Answer 3

1) Adverse immune/hypersensitivity rxns
2) Anaphylaxis
3) Eczema, allergic rhinitis, asthma
4) Environmental allergy
5) Food allergy

Question 4

What are 3 reasons why atopic dermatitis itches?

Answer 4

1) Dry/rough skin
2) Inflamed skin
3) Infection/bacterial load

• MUST identify presence of all the PT presents with to limit symptoms

Question 5

How does skin inflammation present in dark-skinned races?

Answer 5

Darker pigmentation

Question 6

How does the look and feel of skin affect management of a rash/itch?

Answer 6

1) Inflammation → Topical steroids PRN

2) Dry and rough? → ↑Moisturiser use

3) Isolated pimples/pustules far away from “older lesions” → early signs of bacterial ifxn → Antiseptic wash + topic antibiotics PRN + screen caregivers (treat everyone if needed)

Question 7

True or false: Topical treatments for eczema in children can be discontinued upon alleviation of symptoms.

Answer 7

False:
Eczema is characterized by cycles of flare ups and
improvement with treatment
- there is no “cure” for
eczema
- Some children may outgrow eczema (especially if it’s mild),
but many do not
- condition must be controlled long term (better control → ↓symptoms, flared, complications)

Question 8

What are 4 triggers for eczema and their typical presentations/Hx?

Answer 8

1) Sweating
- after playing, on hot day
- ↑moisture not stop exercising, shower child after play

2) Stress
- stress counselling

3) Falling ill
- vax compliance, personal hygiene

4) Food allergy
- avoid allergen

Question 9

True or false: Any patient who needs to use topical steroids several times every week,
should stop steroids immediately to limit risk of toxicity.

Answer 9

False:
They should be re-assessed for moisturiser need and triggers.

Question 10

What is the difference between bacterial load and acute skin infection in eczema?

Answer 10

1) Presentation
B: itchy papules/pimple/pustules may be distant from site of eczema
A: ±golden crusts, fever, flare of eczema

2) Treatment
B: suppression eg. antiseptic washes
A: antibiotics stops after infection resolves then remit to suppression measures as per bacterial load

Question 11

How is eczema/acute bacterial skin infection investigate?

Answer 11

1) Swab lesions for bacterial culture

2) Rx empiric antibiotics when clinically certain until guided by c/s

3) Blood cultures if febrile and toxic-looking (-ve result DOES NOT exclude septicemia)

Question 12

How is infected eczema treated?

Answer 12

Acute: antibiotics for 1-2 weeks
- topical if mild (few areas with no fever)
- if more extensive: Cloxacillin

Control: antiseptic washes
- commence with antibiotics
- wean off slowly AFTER antibiotic course

also review eczema control as this is a complication

Question 13

What are the common causes of isolated urticaria in childhood?

Answer 13

1) Infection
- viruses (<2weeks after initial infection)
- Strep (pharyngitis)
- M. pneumoniae

2) Idiopathic
3) Allergens
- drugs: 5-12%, food 5%

4) Physical
5) Autoimmune

Question 14

How does one differentiate between isolated IgE-mediated and infection-related/idiopathic urticaria?

Answer 14

Onset
IgE: <2hr
I/I: no consistent rs with trigger

Resolution:
IgE: <24 of exposure
I/I: days/weeks

Pattern:
Ige: peaks then disappears
I/I: Waxes/wanes, migrates

Antihistamine response:
IgE: Total/near-total resolution
I/I: Varied

Question 15

True or false: A medically diagnosed egg allergy is a contraindication for MMR and influenza vaccines in singapore.

Answer 15

False: MMR (no egg protein)
but both no impact on vaccination eligibility

Question 15

What is the typical (i) onset (ii) mild (iii) treatment (iv) age to outgrow of egg allergies?

Answer 15

i) (early) infancy
ii) typically mild
iii) avoid eggs
iv) outgrow <~5y/o

Question 16

What is the typical (i) onset (ii) mild (iii) treatment (iv) age to outgrow of peanut allergies?

Answer 16

i) infancy
ii) severe (should carry Epipen)
iii) minority outgrow by 5y/o
iv) Epipen and avoidance of trigger

**10-15% also have tree nut allergies

Question 17

What is the typical (i) onset (ii) mild (iii) treatment (iv) age to outgrow of shellfish allergies?

Answer 17

i) Any age (typically school-aged or older)
ii) variable
iii) outgrowing is rare
iv) avoid trigger

Question 18

What is indicated for a mild anaphylactic rxn?

Answer 18

1 standard dose PO antihistamine (eg. cetrizine, fexofenadine)
- usually resolves within 2 hrs

Question 19

How is anaphylaxis diagnosed and treated?

Answer 19

Clinical diagnosis by any signs of fainting/ dizzy/ hypotensive/ breathing difficulties after allergen exposure

Rx:
IM Adrenaline
± antihistamines

Question 20

Why do anaphylaxis cases need to be admitted/monitored even after IM adrenaline is given?

Answer 20

Biphasic rxn:
- recurrence of symptoms 6-9hrs after