Cutaneous Drug Eruptions Flashcards
When do cutaneous drug eruptions become a diagnostic challenge?
In childhood
Polypharmacy and increased drug use
What types of immunological cutaneous drug eruption can occur? (give an example of each)
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
Are immunological or non-immunological cutaneous drug eruptions dose dependent?
Non-immunological are dose dependent
What non-immunological cutaneous drug eruptions can occur?
Drug induced alopecia Eczema Phototoxicity Skin erosion (topical 5-fluorouracil) Atrophy due to topical steroids
What type of rash do most cutaneous drug eruptions present?
Morbilliform rash: (Type IV) reaction
Measles like
Red maculopapular rash
Generalised and symmetrical
What percentage of patients have an urticaria drug reaction?
5-10%
Does a skin eruption always resolve when the drug is withdrawn?
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
What risk factors are present for drug eruptions?
Age (young adults>infants/elderly) Gender (females >males) Genetics Other disease (viral infection - HIV, cystic fibrosis) Immune status
What chemicals found in drugs are risk factor for drug eruptions?
Β-lactam compounds
NSAIDs
High molecular weight/hapten-forming drugs
If a patient is on multiple drugs, what 3 things must you consider when trying to determine which drug is causing the eruption?
- Which drug is most likely to cause an eruption
- Time interval between exposure and development of skin reaction
- Any history of previous exposure to the same drug?
How soon after taking the drug, would a Type IV exanthematous drug eruption present?
Onset is 4-21 days after first taking drug
What indicates a potentially serious exanthematous drug reaction?
Involvement of mucous membrane and face Facial erythema and oedema Widespread erythema Fever Skin pain Blisters, purpura, necrosis, Lymphadenopathy, arthralgia SOB / wheezing
Give examples of the types of drugs which can cause exanthematous reactions
Penicillins Sulphonamides Erythromycin Allopurinol Anti-epileptics: carbamazepine, phenytoin NSAIDs Chloramphenicol
What two forms of urticarial drug reaction can occur?
immediate IgE-mediated hypersensitivity reaction (Type I) on re-exposure to drug
Direct release of inflammatory mediators from mast cells on first exposure
What type of drugs cause an acneiform reaction?
Glucocorticoids (steroid acne)
Androgens, lithium, isoniazid, phenytoin
What drugs are known to cause Acute generalised exanthematous pustulosis (AGEP)?
Antibiotics, calcium channel blockers, antimalarials
these reactions are RARE
What type of lesions can be seen in acneiform and AGEP reactions?
Pustular or bullous lesions
What drugs can induce Bullous Pemphigoid?
ACE inhibitors, penicillin, furosemide
What drugs can cause Linear IgA disease?
Vancomycin
What does a fixed drug eruption look like?
Well demarcated round/ovoid plaques
Red, painful
Resolves but pigmentation still there when drug stopped
What drugs are known to cause fixed drug eruptions?
Tetracycline, doxycycline
Paracetamol
NSAIDS
Carbamazepine
Give examples of severe adverse cutaneous drug reactions
Stevens-Johnson syndrome (SJS)
Toxic epidermal necrolysis (TEN)
Drug reaction with eosinophilia and systemic symptoms (DRESS)
Acute generalised exanthematous pustulosis (AGEP)
Describe the type of skin phototoxicity caused by chlorpromazine or amiodarone
Immediate prickling with delayed erythema and pigmentation
What type of drugs are known to cause exaggerated sunburn?
Quinine, thiazides, demeclocycline
What skin reaction is caused by calcium channel antagonists?
Exposed telangiectasia
What drug reaction can Psoralens cause?
Delayed 3-5 days erythema and pigmentation
What drugs can cause increased skin fragility (e.g. porphyria Cutanea tarda)
Nalidixic acid
tetracycline
naproxen
amiodarone
What tests can be done to investigate the cause of Type I drug reactions?
Skin prick/intradermal tests for specific drugs
What tests are available for Type IV drug reactions?
Patch and photopatch tests
What drug reaction can proton-pump inhibitors cause?
sub-acute cutaneous lupus
How would you manage a cutaneous drug eruption?
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
