Cutaneous Drug Eruptions

Question 1

When do cutaneous drug eruptions become a diagnostic challenge?

Answer 1

In childhood

Polypharmacy and increased drug use

Question 2

What types of immunological cutaneous drug eruption can occur? (give an example of each)

Answer 2

Type I Anaphylactic
E.g. Urticaria

Type II Cytotoxic
E.g. Pemphigus and Pemphigoid

Type III Immune complex mediated
E.g. purpura/ rash

Type IV Delayed Cell mediated Hypersensitivity (T cells)
E.g. erythema/ rash

Question 3

Are immunological or non-immunological cutaneous drug eruptions dose dependent?

Answer 3

Non-immunological are dose dependent

Question 4

What non-immunological cutaneous drug eruptions can occur?

Answer 4

Drug induced alopecia
Eczema
Phototoxicity
Skin erosion (topical 5-fluorouracil)
Atrophy due to topical steroids

Question 5

What type of rash do most cutaneous drug eruptions present?

Answer 5

Morbilliform rash: (Type IV) reaction

Measles like
Red maculopapular rash
Generalised and symmetrical

Question 6

What percentage of patients have an urticaria drug reaction?

Answer 6

5-10%

Question 7

Does a skin eruption always resolve when the drug is withdrawn?

Answer 7

No

Can depend on:

the half life of the drug
Ability of drug to be retained/ accumulate in tissue
May cross react with a similar drug class

Question 8

What risk factors are present for drug eruptions?

Answer 8

Age (young adults>infants/elderly)
Gender (females >males)
Genetics
Other disease (viral infection - HIV, cystic fibrosis)
Immune status

Question 9

What chemicals found in drugs are risk factor for drug eruptions?

Answer 9

Β-lactam compounds
NSAIDs
High molecular weight/hapten-forming drugs

Question 10

If a patient is on multiple drugs, what 3 things must you consider when trying to determine which drug is causing the eruption?

Answer 10

1. Which drug is most likely to cause an eruption
2. Time interval between exposure and development of skin reaction
3. Any history of previous exposure to the same drug?

Question 11

How soon after taking the drug, would a Type IV exanthematous drug eruption present?

Answer 11

Onset is 4-21 days after first taking drug

Question 12

What indicates a potentially serious exanthematous drug reaction?

Answer 12

Involvement of mucous membrane and face
Facial erythema and oedema
Widespread erythema
Fever
Skin pain
Blisters, purpura, necrosis, Lymphadenopathy, arthralgia
SOB / wheezing

Question 13

Give examples of the types of drugs which can cause exanthematous reactions

Answer 13

Penicillins
Sulphonamides
Erythromycin
Allopurinol
Anti-epileptics: carbamazepine, phenytoin
NSAIDs
Chloramphenicol

Question 14

What two forms of urticarial drug reaction can occur?

Answer 14

immediate IgE-mediated hypersensitivity reaction (Type I) on re-exposure to drug

Direct release of inflammatory mediators from mast cells on first exposure

Question 15

What type of drugs cause an acneiform reaction?

Answer 15

Glucocorticoids (steroid acne)

Androgens, lithium, isoniazid, phenytoin

Question 16

What drugs are known to cause Acute generalised exanthematous pustulosis (AGEP)?

Answer 16

Antibiotics, calcium channel blockers, antimalarials

these reactions are RARE

Question 17

What type of lesions can be seen in acneiform and AGEP reactions?

Answer 17

Pustular or bullous lesions

Question 18

What drugs can induce Bullous Pemphigoid?

Answer 18

ACE inhibitors, penicillin, furosemide

Question 19

What drugs can cause Linear IgA disease?

Answer 19

Vancomycin

Question 20

What does a fixed drug eruption look like?

Answer 20

Well demarcated round/ovoid plaques
Red, painful

Resolves but pigmentation still there when drug stopped

Question 21

What drugs are known to cause fixed drug eruptions?

Answer 21

Tetracycline, doxycycline
Paracetamol
NSAIDS
Carbamazepine

Question 22

Give examples of severe adverse cutaneous drug reactions

Answer 22

Stevens-Johnson syndrome (SJS)
Toxic epidermal necrolysis (TEN)
Drug reaction with eosinophilia and systemic symptoms (DRESS)
Acute generalised exanthematous pustulosis (AGEP)

Question 23

Describe the type of skin phototoxicity caused by chlorpromazine or amiodarone

Answer 23

Immediate prickling with delayed erythema and pigmentation

Question 24

What type of drugs are known to cause exaggerated sunburn?

Answer 24

Quinine, thiazides, demeclocycline

Question 25

What skin reaction is caused by calcium channel antagonists?

Answer 25

Exposed telangiectasia

Question 26

What drug reaction can Psoralens cause?

Answer 26

Delayed 3-5 days erythema and pigmentation

Question 27

What drugs can cause increased skin fragility (e.g. porphyria Cutanea tarda)

Answer 27

Nalidixic acid
tetracycline
naproxen
amiodarone

Question 28

What tests can be done to investigate the cause of Type I drug reactions?

Answer 28

Skin prick/intradermal tests for specific drugs

Question 29

What tests are available for Type IV drug reactions?

Answer 29

Patch and photopatch tests

Question 30

What drug reaction can proton-pump inhibitors cause?

Answer 30

sub-acute cutaneous lupus

Question 31

How would you manage a cutaneous drug eruption?

Answer 31

Discontinue the drug (if possible)
Use an alternative
Antihistamines may help if Type I or with symptoms of itch
Allergy bracelets are useful for some drugs