Drug reactions/blistering Flashcards by Emily Zaniker

What are the most common form of drug reactions?

Exanthematous-type drug reactions

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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

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What drugs commonly cause exanthematous-type drug reactions?

-lactam antibiotics (the penicillins), sulfonamide antimicrobials, nonnucleoside reverse transcriptase inhibitors, and antiepileptic medications

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What drug-viral interactions increase susceptibility to exanthematous-type drug reactions?

Infectious mononucleosis + aminopenicillin

HIV + sulfonamides

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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)

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What systemic features can indicate a potentially severe drug reaction?

Fever, organ involvement, cough, pharyngitis, lymphadenopathy, arthralgia

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What cutaneous clinical features may indicate a severe drug reaction?

Erythroderma, prominent facial involvement, swelling/edema, mucous membrane involvement, skin tenderness, blistering, shedding, purpura

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What is the mechanism of epidermal necrolysis?

Widespread apoptosis of keratinocytes provoked by activation of a cell-mediated cytotoxic reaction and amplified by cytokines

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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

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What are the pathological features of epidermal necrolysis?

Full-thickness necrosis of epiderms wit mild mononuclear cell infiltrate

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What is the treatment for epidermal necrolysis?

Early identification, withdrawal of suspect drugs, symptomatic treatment

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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

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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

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What is the presentation of erythema multiforme major?

Typical and/or occasionally atypical papular target lesions with severe mucosal invovlement and systemic features

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What are the most common triggers of erythema multiforme?

A preceding HSV or mycoplasma pneumonia infection

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What are the symptoms of stevens-johnson syndrome/toxic epidermal necrolysis?

Prodrome of upper respiratory tract symptoms, fever, and painful skin

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What differentiates stevens-johnson syndrome from toxic epidermal necrolysis?

SJS is <10% body surface, TEN >30% body surface (in between is SJS-TEN)

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What are the most common drugs to cause stevens-johnson syndrome/toxic epidermal necrolysis?

NSAIDs, antibiotics, antiepileptics

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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)

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What is the optical medical treatment of stevens-johnson syndrome/toxic epidermal necrolysis?

Therapies that selectively block keratinocyte apoptosis like IVIg and supportive care

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What is the mechanism by which acute eczema and stasis pressure cause cells to separate from one another?

Edema/spongiosis/hydrostatic pressure

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What is the mechanism by which pemphigus causes cells to separate from one another?

Acantholysis (loss of desmosomes)

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What is the mechanism by which viral infections and sunburns cause cells to separate from one another?

Cellular degeneration

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What is the mechanism by which friction blisters and hereditary mechanobullous disorders cause cells to separate from one another?

Cytolysis

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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

What are the microscopic/histologic features of dermatitis herpetiformis?

Neutrophilic microabscesses, granular IgA deposits on normal looking skin

What is the treatment for dermatitis herpetiformis?

Dapsone therapy on the rash

What are the key associations to dermatitis herpetiformis?

Gastric atrophy, thyroid disease, small bowel lymphoma, + anti-gliadin, anti-transglutaminase antibodies

What are the general characteristics of phemphigus disorders?

A group of autoimmune blistering diseases characterized by intraepidermal blisters due to loss of cell-cell adhesion of keratinocytes (histology) and the finding of in vivo bound and circulating IgG autoantibodies directed against the surface of keratinocytes

What are the three major forms of pemphigus?

Pemphigus vulgaris, pemphigus foliaceus, and paraneoplastic pemphigus

What is the cause of pemphigus vulgaris?

Functional inhibition of desmogleins that play an important role in cell-cell adhesion of keratinocytes, mediated by IgG autoantibodies against desmoglein 3

What is the cause of pemphigus foliaceus?

Functional inhibition of desmogleins via IgG autoantibodies against desmoglein 1

What is the cause of paraneoplastic pemphigus?

A blistering disease mediated by IgG autoantibodies against plakin molecules and desmogleins

What is the classic clinical presentation of pemphigus vulgaris?

Erosions on mucous membranes and skin with flaccid blisters on skin

What is the classical clinical presentation of pemphigus foliaceus?

Crusted, scaly skin lesions

What is the treatment for pemphigus generally?

Topical and systemic corticosteroids and immunosuppressive agents

What is the cause of bullous pemphigoid?

It is caused by tissue-bound and circulating autoantibodies against the BP antigen 180 and BP antigen 230, which are part of hemidesmosomes that promote dermo-epidermal cohesion

What is the typical clinical presentation of bullous pemphigoid?

Intensely pruritic eruptions with widespread blisters, may also have excoriated, eczematous, or urticarial lesions

What are porphyrias?

Heterogenous group of metabolic diseases resulting from an inherited or acquired dysfunction in enzymes of heme biosynthesis

What is the cause of porphyria cutanea tarda?

Decreased catalytic activity of uroporphyrinogen decarboxylase

What are the cutaneous manifestations of porphyria cutanea tarda?

Increased photosensitivity of skin, skin fragility, possible blistering, erosions, crusts, milia, scars in sun exposed sites, hypertrichosis, scarring alopecia, and morpheaform and sclerodermoid changes

What diseases are associated with porphyria cutanea tarda?

Underlying liver disease (via alcoholism or hepatitis C)

Which of the following is among the common causes of Stevens-Johnson syndrome? a) syphillis b) pneumococcal pneumoniae c) cytomegalovirus d) phenytoin e) herpes simplex virus

d) phenytoin * anti-epileptic drug*

Porphyria cutanea tarda is associated with: a) Chron's disease b) ulcerative colitis c) hepatitis C d) polycystic ovarian disease e) polycystic kidney disease

c) hepatitis C

Pemphigus vulgaris is an autoimmune blistering disease characterized by flaccid bullae and erosions and IgG antibodies directed against proteins associated with: a) type IV collagen b) hemidesmosomes c) type VII collagen d) desmosomes e) microtubules

d) desmosomes

What type of reaction is this?

Urticarial reaction

HPI: 35 y.o. man who presented to clinic with sore throat and fatigue. He was diagnosed with acute pharyngitis and started on amoxicillin for empiric treatment. A few days later he presented to clinic with this rash. What type of reaction is this?

Exanthematous reaction

What type of rash is described as "morbilliform"?

Measles

What is the classic progression of measles?

A morbilliform rash starting from the head and spreading down the body

What is the cause of roseola infantum?

HHV 6

What is the clinical course of roseola infantum?

Starts with a high fever and ends abruptly, pinkish-red flat or raised rash appears on the trunk/body around when fever ends

HPI: 12 y.o. boy with a seizure disorder was recently started on phenytoin. Three weeks later he felt unwell with fever and malaise. His rash is below. He has a high WBC count, high eosinophils, and high AST levels. What is his most likely diagnosis?