Clinical: Cutaneous Reactions Flashcards
Pathogenesis of allergic contact dermatitis
Type IV hypersensitivity causing eczematous reaction in the skin to an allergen
Presentation of allergic contact dermatitis
Acute: vesicles, bullae
Subacute: microvesicles, erythema, scale
Chronic: lichenification, scaling, erythema
Unique pattern of allergic contact dermatitis caused by plants
Linear nature of vesicle distribution
4 most common shampoo allergens that cause allergic contact dermatitis
Cocamidylpropyl Betaine
Fragrance
Formaldehyde Releasers
MCI (Miss Chinese International pageant)
Diagnositc test for allergic contact dermatitis
Patch Test
Treatment for allergic contact dermatitis
Short Term topical corticosteroids
Antihistamines
Pathogenesis of Irritant Contact Dermatitis
Eczematous reaction secondary to exposure to a harsh product (alkali) or repeated exposure to a mild irritant (water)
Treatment for Irritant Contact Dermatitis
Avoid the irritant
Pathogenesis of Phytophotodermatitis
Reaction to furocoumarins in certain plants (limes). Reaction only occurs once the patient is exposed to UV light.
-erythema, edema, hyperpigmentation
Most common scenario for Morbilliform Drug Eruption
Patient with mono put on ampicillin has a drug reaction. Systemic pruritis and erythema.
Treatment for Morbilliform Drug Eruption
Topical steroids, systemic antihistamines
-remove offending medication
Pathogenesis of Drug Hypersensitivity Syndrome
AKA Drug Rash with Eosinophilia and Systemic Symptoms (DRESS)
- drug causing eosinophilic reaction in the body creating a rash and chance of internal organ (liver) inflammation
- can be a life threatening condition
How is DRESS different from Morbilliform eruption?
Morbilliform will have normal Liver Function Tests, no eosinophilia, lack of fever and lymphadenopathy
Pathogenesis of Stevens-Johnson syndrome (SJS)
Hypersensitivity reaction to drugs (or infections) leading to dermoepidemal junction cell death causing the epidermis to separate from the dermis
Treatment for Stevens-Johnson Syndrome
Corticosteroids early
Pathogenesis of Toxic Epidermal Necrolysis (TEN)
Hypersensitivity reaction to drugs (or infections) leading to dermoepidemal junction cell death causing the epidermis to separate from the dermis
How are SJS and TEN different?
They are the exact same thing. SJS involves only about 10% of the skin. If more than 30% of the skin is involved the name changes to TEN.
What is a fixed drug eruption?
Annular, erythematous plaque that forms on the skin in the exact same spot every time a patient takes a certain medication.
Culprit in any Urticaria
Mast cells
Classification of Urticaria
Acute: occurring for less than 6 weeks
Chronic: occurring for more than 6 weeks, at least 2x a week
Episodic: occurring longer than 6 weeks but less than 2x a weeks
Most common known cause of Acute Urticaria
Upper Respiratory Tract infection (usually strep)
Treatment for Dermatographism
Antihistamines
Cause of Cholinergic Urticaria
Any activity that raises core body temperature
also treat with antihistamines
Most common cause of Solar Urticaria
UVA exposure
Rash pattern and cause of Erythema Multiforme
Targetoid Lesion
Most commonly caused by HSV
Rash pattern of Erythema Nodosum
Symmetric, tender, red nodules usually on anterior legs (type of septal panniculitis or SubQ fat inflammation)
Most common cause of erythema nodosum in children
Strep infection
Most common causes of erythema nodosum in adults
Infection
Drugs
Sarcoidosis
Autoimmune Diseases
What is the “id” reaction
AKA Autosensitization Dermatitis
A widespread eczematous reaction occurring secondary to a severe primary dermatitis
Most common cause of “id” reactions
Severe Stasis dermatitis
Most common cause of Chronic Autoimmune Urticaria
Patients have IgG Abs to the Fc portion of IgE
