cutaneous drug eruptions Flashcards
what are they?
side effects of skin - account for 30% of drug reactions
what is the issue with them?
they mimic other skin diseases and are becoming more common due to increase in drug usage and polypharmacy
2 types of cutaneous drug reactions
immunological reactions
non-immunological
what is the presentation of immunological reactions
allergic, not dose-dependent Type 1 = anaphylaxis, urticaria Type 2 = cytotoxic reactions (pemphigus and pemphigoid) Type 3 = purpura rash Type 4 = rash, erythema
what is the presentation of non-immunological reactions
Mostly exanthematous, morbilliform, maculopapular Occasionally is urticaria Also can be papulosquamous, pustular, bullous, pigmentation, itch, pain, photosensitivity CONSIDER any patient taking medication who suddenly develops a SYMMETRICAL skin eruption
How do you identify the problematic drug when the patient is on multiple drugs?
- Identify drug that is known to be the most likely to cause an eruption
- Time the interval between exposure and development of the skin reaction
- Look at history of previous exposure to the same drug
what is a exanthematous drug eruption?
most common type of drug eruption - 90%
How does exanthematous drug eruption present?
Widespread symmetrically distributed rash, distinctive [idiosyncratic], type IV reaction
Usually nothing on mucous membranes
Onset is 4-21 days after first taking drug
Usually mild and self-limiting
Itch and mild fever are common
Can progress to a severe, life-threatening reaction
what are the indicators an exanthematous drug eruption will be severe?
involvement of face and mucous membrane, facial erythema and oedema, widespread confluent erythema, fever >38.5°C, skin pain, blisters, purpura, necrosis, lymphadenopathy, arthralgia, SOB, wheezing
What drugs are associated with exanthematous drug eruptions?
penicillins sulphonamides erythromycin streptomycin allopurinol anti-epileptics NSAIDs chloramphenicol
what is a urticarial drug eruption?
usually a type 1 reaction after re-challenge with drug
OR
direct release of inflammatory mediators from mast cells on first exposure i.e. NO hypersensitivity reaction
how does a urticarial drug eruption present?
can be associated with angioedema or anaphylaxis
what is a pustular/bullous drug eruption?
linear IgA disease
ranges from mild to severe
what drugs can cause drug-induced bullous pemphigoid?
Gliptins
penicillin
furosemide
What is acneiform and what drugs can cause it?
steroid acne caused by androgens lithium isoniazid phenytoin
What is AGEP and what drugs cause it?
acute generalised exanthematous pustulosis
it's very rare caused by antibiotics CCBs anti-malaria drugs
what is a fixed drug eruption?
a well demarcated round/ovoid plaque
how does a fixed drug eruption present?
Can present as eczematous lesions, papules, vesicles or urticaria
Residues with PERSISTENT pigmentation when the drug is stopped
On hands, genitals, hips, sometimes oral mucosa
Can reoccur at same site on re-exposure to drug
Red and painful
what drugs can cause a fixed drug eruption?
tetracycline
doxycycline
NSAIDs
caramazepine
name 4 severe drug reactions which have cutaneous and systemic symptoms
Stevens-Johnson syndrome (SJS )
toxic epidermal necrolysis (TEN)
Drug reaction with eosinophilia and systemic syndrome (DRESS)
Acute generalised exanthematous pustulosis (AGEP)
What is a phototoxic drug reaction?
a non-immunological reaction that happens when someone is exposed to enough phot-reactive drug and light of the appropriate wavelengths (usually UVA/visible light)
what causes a phototoxic drug reaction?
drugs
immunosuppression/lupus
all can cause an increased sensitivity to sunlight
How does an acute phototoxic reaction present?
skin toxicity
- phototoxicity
- systemic toxicity
- photo-degradation
how does chronic phototoxic reaction present?
pigmentation
photoageing
photocarcinogeneis
