Cutaneous Drug Eruptions Flashcards

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1
Q

When do cutaneous drug eruptions become a diagnostic challenge?

A

In childhood

Polypharmacy and increased drug use

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2
Q

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

A

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

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3
Q

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

A

Non-immunological are dose dependent

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4
Q

What non-immunological cutaneous drug eruptions can occur?

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

What type of rash do most cutaneous drug eruptions present?

A

Morbilliform rash: (Type IV) reaction

Measles like
Red maculopapular rash
Generalised and symmetrical

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6
Q

What percentage of patients have an urticaria drug reaction?

A

5-10%

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7
Q

Does a skin eruption always resolve when the drug is withdrawn?

A

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

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8
Q

What risk factors are present for drug eruptions?

A
Age (young adults>infants/elderly)
Gender (females >males)
Genetics
Other disease (viral infection - HIV, cystic fibrosis)
Immune status
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9
Q

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

A

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

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10
Q

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

A
  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?
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11
Q

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

A

Onset is 4-21 days after first taking drug

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12
Q

What indicates a potentially serious exanthematous drug reaction?

A
Involvement of mucous membrane and face
Facial erythema and oedema
Widespread erythema
Fever
Skin pain
Blisters, purpura, necrosis, Lymphadenopathy, arthralgia
SOB / wheezing
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13
Q

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

A
Penicillins
Sulphonamides
Erythromycin
Allopurinol
Anti-epileptics: carbamazepine, phenytoin
NSAIDs
Chloramphenicol
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14
Q

What two forms of urticarial drug reaction can occur?

A

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

Direct release of inflammatory mediators from mast cells on first exposure

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15
Q

What type of drugs cause an acneiform reaction?

A

Glucocorticoids (steroid acne)

Androgens, lithium, isoniazid, phenytoin

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16
Q

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

A

Antibiotics, calcium channel blockers, antimalarials

these reactions are RARE

17
Q

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

A

Pustular or bullous lesions

18
Q

What drugs can induce Bullous Pemphigoid?

A

ACE inhibitors, penicillin, furosemide

19
Q

What drugs can cause Linear IgA disease?

A

Vancomycin

20
Q

What does a fixed drug eruption look like?

A

Well demarcated round/ovoid plaques
Red, painful

Resolves but pigmentation still there when drug stopped

21
Q

What drugs are known to cause fixed drug eruptions?

A

Tetracycline, doxycycline
Paracetamol
NSAIDS
Carbamazepine

22
Q

Give examples of severe adverse cutaneous drug reactions

A

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

23
Q

Describe the type of skin phototoxicity caused by chlorpromazine or amiodarone

A

Immediate prickling with delayed erythema and pigmentation

24
Q

What type of drugs are known to cause exaggerated sunburn?

A

Quinine, thiazides, demeclocycline

25
Q

What skin reaction is caused by calcium channel antagonists?

A

Exposed telangiectasia

26
Q

What drug reaction can Psoralens cause?

A

Delayed 3-5 days erythema and pigmentation

27
Q

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

A

Nalidixic acid
tetracycline
naproxen
amiodarone

28
Q

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

A

Skin prick/intradermal tests for specific drugs

29
Q

What tests are available for Type IV drug reactions?

A

Patch and photopatch tests

30
Q

What drug reaction can proton-pump inhibitors cause?

A

sub-acute cutaneous lupus

31
Q

How would you manage a cutaneous drug eruption?

A

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