Drug reactions/blistering Flashcards
What are the most common form of drug reactions?
Exanthematous-type drug reactions
What is the typical presentation of an exanthematous-type drug reaction?
Eruptions that start on the trunk and spread peripherally in a symmetric fashion with pruritis, usually occur within one week of taking a drug, and usually resolves within 1-2 weeks
Changes in color from bright red to dark red
What drugs commonly cause exanthematous-type drug reactions?
-lactam antibiotics (the penicillins), sulfonamide antimicrobials, nonnucleoside reverse transcriptase inhibitors, and antiepileptic medications
What drug-viral interactions increase susceptibility to exanthematous-type drug reactions?
Infectious mononucleosis + aminopenicillin
HIV + sulfonamides
What conditions can start with exanthematous eruption and then lead to more systemic disease?
Hypersensitivity syndrome/reaction, drug reaction with eosinophilia and systemic symptoms (DRESS)
What systemic features can indicate a potentially severe drug reaction?
Fever, organ involvement, cough, pharyngitis, lymphadenopathy, arthralgia
What cutaneous clinical features may indicate a severe drug reaction?
Erythroderma, prominent facial involvement, swelling/edema, mucous membrane involvement, skin tenderness, blistering, shedding, purpura
What is the mechanism of epidermal necrolysis?
Widespread apoptosis of keratinocytes provoked by activation of a cell-mediated cytotoxic reaction and amplified by cytokines
What is the presentation of epidermal necrolysis?
Confluent purpuric and erythematous macules evolving to flaccid blisters and epidermal detachment predominating on the trunk and upper limbs and associated with mucous membrane involvement
What are the pathological features of epidermal necrolysis?
Full-thickness necrosis of epiderms wit mild mononuclear cell infiltrate
What is the treatment for epidermal necrolysis?
Early identification, withdrawal of suspect drugs, symptomatic treatment
What are the two types of target lesions in erythema multiforme?
Typical papular lesions with at least three different zones or atypical papular lesions with two zones and/or poorly defined borders
What is the presentation of erythema multiforme minor?
Typical and/or occasionally atypical papular targetlesions with little to no mucosal involvement and no systemic symptoms
What is the presentation of erythema multiforme major?
Typical and/or occasionally atypical papular target lesions with severe mucosal invovlement and systemic features
What are the most common triggers of erythema multiforme?
A preceding HSV or mycoplasma pneumonia infection
What are the symptoms of stevens-johnson syndrome/toxic epidermal necrolysis?
Prodrome of upper respiratory tract symptoms, fever, and painful skin
What differentiates stevens-johnson syndrome from toxic epidermal necrolysis?
SJS is <10% body surface, TEN >30% body surface (in between is SJS-TEN)
What are the most common drugs to cause stevens-johnson syndrome/toxic epidermal necrolysis?
NSAIDs, antibiotics, antiepileptics
What is the mechanism of exfoliation in stevens-johnson syndrome/toxic epidermal necrolysis?
Extensive death of keratinocytes via apoptosis, mediated by interaction of Fas-Fas Ligand (death receptor and ligand pair)
What is the optical medical treatment of stevens-johnson syndrome/toxic epidermal necrolysis?
Therapies that selectively block keratinocyte apoptosis like IVIg and supportive care
What is the mechanism by which acute eczema and stasis pressure cause cells to separate from one another?
Edema/spongiosis/hydrostatic pressure
What is the mechanism by which pemphigus causes cells to separate from one another?
Acantholysis (loss of desmosomes)
What is the mechanism by which viral infections and sunburns cause cells to separate from one another?
Cellular degeneration
What is the mechanism by which friction blisters and hereditary mechanobullous disorders cause cells to separate from one another?
Cytolysis
What is the mechanism by which immunobullous disorders cause cells to separate from one another?
Basement membrane disruption
How can you tell the difference between intraepidermal and subepidermal blisters?
Intraepidermal blisters = flaccid, easily broken
Subepidermal blisters = tense and usually intact
distinguish with the Niklosky sign
What is the niklosky sign?
A test where you push on the skin and see if there is epidermal separation by lateral pressure to edge of blister or to normal appearing skin, which is characteristic of intraepidermal blisters
What lab test should be done to evaluate for bullous tinea?
KOH
What is a Tzanck test used for?
To evaluate for multinucleated cells (Herpes) and acantholytic cells (pemphigus)
What are the clinical features of dermatitis herpetiformis?
Intensely itchy, chronic papulovesicular eruption distributed symmetrically on extensor surfaces, buttocks, and back with microabscesses