261. Drug Rxns / Blistering Disorders Flashcards
Immediate vs. Delayed vs. Urticarial Reaction
Immediate: <1 hr dose, urticaria (hives), angioedema (ACE-i’s), anaphylaxis
Delayed: >6hrs (wks/mos), exanthem eruptions, systemic rxns, vasculitis
Urticarial: usually not drugs (post-infectious, idiopathic) unless immediate rxn to pain meds
What is exanthem?
Exanthematous Drug Rxns
Location, Look, Timeline, Tx
Rapidly erupting rash with dx features similar to infectious disease (morbilliform = like measles)
Most common of all skin eruptions, limited to skin (trunk/extremities) macules/papules, pruritis, fever
Lesions appear 7-10 days after med, disappear after discontinuation
Tx: topical steroids, oral antihistamines, reassurance
Drug Induced Hypersensitivity Syndrome
what it is, signs/sx, course, meds, tx
Drug Rxn with Eosinophilia + Systemic Sx (DRESS)
Skin eruption with fever/organ involvement (liver, kidney heart)
Macular exanthem, centrofacial swelling, fever, malaise, lymphadenopathy
C: 3rd week of adding med/changing dose, may persist for many weeks after cessation
M: ABx, anticonvulsants, NSAIDs
Tx: stop all nonessential/suspect meds
mild - topical steroids, systemic antihistamines
Severe: systemic steroids/taper (prednisone)
Erythema Multiforme Major
what it is, EM Minor, precipitating factor
Self-limited/potentially recurrent
Abrupt onset of papular target lesions <24hrs favoring acrofacial sites
EM Minor: assoc w/ HSV, no mucosal involvement, no systemic sx
Major: Severe mucosal involvement, systemic features (conjuctival, psedomembrane tongue, oral/vulvar erosions
Trigger: Preceding HSV, mycoplasma pneumonia (NOT DRUG)
No risk of TEN progression
Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis
What it is, timeline, meds, findings, tx
Mucocutaneous tenderness (pain), erythema, extensive skin erosions/necrosis (detachment of epidermis at mucosal surfaces)
SJS: <10% body surface area
TEN: >30%
Meds: Sulfa ABx, anticonvulsants, NSAIDs
CM: fever, rhinitis, myalgia, symmetric eruption on face/trunk/extremities, involves mucous membranes, atypical target lesions, extensive skin sloughing, dusky appearance
Tx: early recognition and stopping drug
Flaccid v. Tense Blister
Flaccid = intraepidermal (+Nikolsky Sign = separates from lateral pressure) Tense = subepidermal
Dermatitis herpetiformis
cause, skin, path, DIF, Tx, Pathophysiology
Gluten sensitivity
p: Genetic + High Gluten Diet = form IgA to gluten transglutaminase = IgA crosses over to skin transglutaminase = deposit of complexes in dermis = lesions
Skin: pruritic papulovesicles on extensor surfaces/butt/back
Path: neutrophil inflammation of dermal papillae, vesicles at dermal-epidermal junction
DIF: +IgA deposition in dermal papillae
Tx: Gluten-Free Diet/Dapsone
Pemphigus Vulgaris
(What it is, age, Skin, DIF, Path, Tx)
Pemphigus Foliaceous
Auto-Ab to desmogleins in desmosome = superficial bullae (easily ruptured) on skin/mucous membranes
Age: Elderly - 5th/6th decade
DIF: chicken-wire appearance of +IgG against Dsg3/1 (part of desmosome)
Path: intraepidermal splitting/separation just above basal keratinocytes
Tx: immunosuppression (prednisone, imuran, rituximab)
P. foliaceous: more superficial, blisters just under corneum due to anti-Dsg1 (only on outer layers of epidermis)
Bullous Pemphigoid
What it is, age, skin, tx, path, DIF
Auto-Ab to hemidesmosome = deep, large, tense bullae on flexural surfaces
Age: Elderly (60-70s)
Path: subepidermal split
DIF: +IgG/C3 at basement membrane zone
Tx: Prednisone, azatioprine, tetracycline, dapsone
Porphyria Cutanea Tardae
What it is, skin, non-skin, trigger, dx
Disorder in heme synthesis enzyme pathway (uroporphyrinogen decarboxylase) = photosensitivity/skin fragility
Skin: blisters, erosions, crusts, sars in sun-exposed sites - usually dorsal hand
Non-skin: hypertrichosis, scarring alopecia, morpheaform/sclerodermoid changes
Trigger/Assoc with Alcoholism/Hep C liver disease at sx onset
Dx: Urine porphyrins that fluoresce PINK under wood’s light
