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Does a skin eruption always resolve when the drug is withdrawn?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