Skin Reactions

Question 1

What is urticaria?

Answer 1

Hives

Question 2

Describe urticaria?

Answer 2

Lesions appear with 1 hours and last 2-6 hours
Due to mast cell granulation
Type 1 (IgE)> mast cell degranulation> histamine
Dermal oedema

Question 3

What is the difference between urticaria and eczema?

Answer 3

Urticaria=well defined, smooth surface

Eczema= ill defined, scaly surface

Question 4

What is angioedema?

Answer 4

Swelling of subcutaneous tissue or mucous membranes

Not itchy

Question 5

What is anaphylaxis?

Answer 5

Airway, breathing, circulatory problems

Question 6

What is the diagnostic test for type 1 hypersensitivity reactions?

Answer 6

Skin prick testing
Challenge testing
Serum mast cell tryptase level (anaphylaxis)

Question 7

Management for type 1 hypersensitivity skin reactions?

Answer 7

Antihistamines (prevent mast cell degranulation)
Corticosteroids (anti inflammatory)
Adrenaline (for anaphylaxis)

Question 8

What is toxic epidermal necrolysis?

Answer 8

When >30% of skin is effected
Widespread epidermal blistering and sloughing
Drug induced
Keratinocyte death resulting in epidermal detachment at the dermo-epidermal junction

Question 9

What is maculopapular drug eruption?

Answer 9

o Widespread symmetrical erythematous maculopapular rash
o Onset is 4-21 days after first taking drug
o Normally itchy and mild fever
o Due to Penicillin commonly

Question 10

What are the indicators that there is a severe reaction of maculopapular drug eruption?

Answer 10

o Mucous membrane involved
o Fever >38.5
o Looks worse [blistering, facial oedema etc

Question 11

What is erythema nodosum?

Answer 11

o Painful or tender dusky blue-red nodules on shins
o Common in young female adults
o Associated with arthralgia, malaise and fever

Question 12

What causes erythema nodosum?

Answer 12

STOPTED
S = Sarcoidosis
P = Pregnancy
O = Oral contraceptive
T = Tuberculosis
T = Throat infections (strep)
E = Everything else (IBD, non-hodgekin lymphoma etc.)
D = Drugs (sulphonamides eg. co-trimoxazole)

Question 13

What is the management for erythema nodosum?

Answer 13

Underlying cause + NSAIDs

Resolves spontaneously

Question 14

What is erythema multiform?

Answer 14

• Type IV hypersensitivity rash of acute onset due to infection or drugs
Hallmark:
– Target lesion
– Dark/dusky central area with surrounding red rings

Question 15

What causes erythema multiform?

Answer 15

• Herpes simplex virus (most common)
• Mycoplasma pneumoniae (often in children)
Associated with sulphonamide drugs, NSAIDs and phenytoin

Question 16

What is a fixed drug reaction?

Answer 16

The same area of skin is affected every time

Red, round, painful plaques triggered by tetracycline, NSAIDs, paracetamol

Question 17

What is acneiform?

Answer 17

Drug induced acne
glucocorticoids
No comedones like normal acne

Question 18

What eruptions do ACEi cause?

Answer 18

Drug induced bullous pemphigoid (hive-like rash)

Question 19

What is Stevens-johnson syndrome?

Answer 19

Necrosis of the epidermis

Question 20

What are photo toxic drug reactions?

Answer 20

When a drug becomes activated by sunlight and causes damage to the skin

Results in increased sensitivity to sunlight (usually UVA)

Question 21

What drugs commonly cause photo toxic drug reactions?

Answer 21

Doxycycline, Amiodarone, Quinine, Chlorpromazine

Question 22

What are the sings of phototoxic drug reactions?

Answer 22

o Erythema
o Prickling
o Pigmentation
o Increased skin fragility

Question 23

What are the investigations for phototoxic drug reactions?

Answer 23

o - Photo-testing
o - Skin biopsy
o - Photo-patch (for type IV)
o - Skin prick (only type I)

Question 24

What is the management for phototoxic drug reactions?

Answer 24

o - No more drug
o - Topical steroids (heal the skin)
o - Anti-histamines (for itch [type 1])

Question 25

Most common causative organism of celulitis?

Answer 25

strep. pyrogens

Question 26

what is impetigo?

Answer 26

Acute bacterial skin infection-usually affects lips “honey crusted lesions”.
Caused by staph aureus
Commonly seen in children