Dermatology: Drug Eruptions Flashcards
Types of drug reactions affecting the skin?
Immunologically-mediated reaction (allergic) - these are NOT DOSE-DEPENDENT
Non-immunologically mediated reaction (non-allergic) - these CAN be DOSE-DEPENDENT
Types of immunologically mediated reactions and examples of each?
Type I - anaphylactic reactions:
Urticaria
Type II - cytotoxic reactions:
Pemphigus & pemphigoid
Type III - immune complex-mediated reactions:
Purpura/rash
Type IV - cell-mediated delayed hypersensitivity reactions:
T-cell mediated
Erythema/rash
Examples of non-immunologically mediated reactions?
Eczema Drug-induced alopecia Phototoxicity, e.g: doxycycline Skin erosion or atrophy from topically applied steroids Psoriasis Pigmentation Cheilitis, xerosis
Morphologies/presentation of drug reactions?
Exanthematous/morbilliform/maculopapular
Urticarial
Papulosquamous/pustular/bullous
Can present with:
Pigmentation
Itch/pain
Photosensitivity
Who may had a drug reaction?
Any patient who is taking mediation and develops a SYMMETRIC skin eruption of sudden appearance
Exception to the rule “reactions normally resolve when the drug is withdrawn”?
Half-life of the drug plays a role
Ability of the drug to be retained/accumulated in tissues, e.g: highly lipid-soluble drugs
Cross-reaction with a similar class of drugs
Risk factors for development of drug eruptions?
Age - young adults more so than infants/elderly (however, reactions occur in the elderly more, due to increased drug usage)
Gender - females more than males
Genetics
Concomitant disease, e.g: viral infection (HIV/EBV/CMV), cystic fibrosis
Immune status - previous drug reaction or positive skin test
For a patient on multiple drugs, what should be considered?
Drug that is known to be most likely to cause an eruption
The time interval between exposure and development of skin reaction
History of previous exposure to the same drug (sometimes, they may develop a reaction on subsequent uses)
What are exanthematous drug eruptions?
Most common type of drug eruption (90%)
Idiosyncratic, T-cell mediated delayed type hypersensitivity (Type IV) reaction
Features of exanthematous drug eruptions?
Usually mild & self limiting but involves:
Widespread, symmetrically distributed rash
Mucous membranes usually being spared
Pruritus and mild fever are common
Onset is 4-21 days after first taking drug and may progress to a severe life-threatening reaction
Red flag symptoms in exanthematous drug eruptions?
Involvement of mucous membrane and face
Facial oedema & erythema
Widespread confluent erythema; may see Nikolsky sign (gentle pressure lifts skin)
Fever (>38.5⁰C)
Blisters, purpura, necrosis
Lymphadenopathy, arthalgia
Shortness of breath, wheezing
Drugs assoc. with exanthematous drug eruptions?
Penicillins
Sulphonamide antibiotics
Erythromycin
Streptomycin
Allopurinol
Anti-epileptics: carbamazepine
NSAIDs
Phenytoin
Chloramphenicol
What is an urticarial reaction?
Usually an immediate IgE-mediated hypersensitivity reaction (Type I) after re-challenge with the drug, e.g: β-lactams
OR
Direct release of inflammatory mediators from mast cells on first exposure, e.g: aspirin, opiates, NSAIDs
Drugs that can cause an acne-like reaction?
Glucocorticoids (steroid acne)
Androgens (therapeutic), lithium, phenytoin
Drugs that cause acute generalised exanthematous pustulosis (AGEP)?
Sheets of sterile putsules (negative culture); these are reactions that can occur due to antibiotics, CCBs and anti-malarials
Examples of pustular/bullous drug eruptions?
Vesicular/bullous reactions can range from mild-severe, e.g:
Drug-induced bullius pemphigoid (normally in the elderly) - ACE inhibitors penicillin and furosemide
Linear IgA disease can be triggered by drugs like vancomycin
What are fixed drug eruptions?
Reaction that always re-occurs in the same area with the same drug
Appearance of fixed drug eruptions?
Welll-demarcated round/ovoid plaques; they are red and painful and often occur at the hands, genitalia, lips and, sometimes, oral muscosa
Could present as eczematous lesions, papules, vesicles or urticaria
These resolve with persistence pigmentation when the drug is stopped
Drugs assoc. with FDEs?
Tetracycline, doxycycline
Paracetamol
NSAIDS
Carbamazepine
2 types of severe cutaneous adverse reactions and causes?
Stevens-Johnson syndrome (SJS)
Toxic epidermal necrolysis (TEN)
E.g: caused by sulfonamide antibiotics, NSAIDs, phenytoin, cephalosporins and carbamazepine, etc
Drug reaction with eosinophilia and systemic symptoms (DRESS) is characterised by facial oedema and a very high eosinophil count:
Sulfonamides, anti-convulsants, allopurinol, NSAIDs, vancomycin, abacavir
Acute generalised exanthematous pustulosis (AGEP)
Acute and chronic phototoxic drug reaction examples?
Acute:
Skin toxicity
Systemic toxicity
Photodegradation
Chronic:
Pigmentation
Photoageing
Photocarcinogenesis
What are phototoxic cutaneous drug reactions?
Non-immunological mediated skin reaction which will arise in any individual providing there is enough photo-reactive drug and the appropriate wavelength of light (UVA is usually of concern and can occur through window glass)
Increased sensitivity to sunlight, caused by drugs, can also occur via other mechanisms, e.g: immunosuppression
Major patterns of cutaenous phototoxicity?
Immediate prickling with delayed erythema and pigmentation, e.g: chlorpromazine, amiodarone
Exaggerated sunburn, e.g:
quinine, thiazides, DCMT
Exposed telangiectasia, e.g:
CCBs
Delayed 3-5 days erythema and pigmentation, e.g: psoralens
Increased skin fragility, e.g:
nalidixic acid, tetracycline naproxen, amiodarone
Information to ask in history?
Detailed description of reaction
Timing of onset of symptoms in relation to drug administration:
Previous exposure to drug
When did the drug start (in relation to symptoms)
When was the drug stopped
Did stopping the drug affect the symptoms
Photograph of reaction?
Why was the drug being taken:
Underlying illness
Comprehensive drug history including prescribed/non prescribed and herbal/alternative remedies
Previous history of drug reaction, allergy or other illnesses
Why is skin testing NOT INDICATED for serum sickness reactions (Type III) or for T-cell mediated reactions (Type IV)?
Can trigger SJS, TEN or DRESS
Management of drug eruptions?
Discontinue the drug (if possible) and use an alternative (class if able to)
Topical steroids, anti-histamines may be useful may be useful.
Allergy bracelets are useful for some drugs
