Small Animal Dermatology, 3rd edition

CHAPTER 17 CUTANEOUS ADVERSE DRUG REACTION 273

Pathogenesis unclear: may involveα/βCD4+Th

1 cells and CD8

+cytotoxic

effector cells

Considered to involve a variety of mechanisms such as the upregulation of

expression of MHC II and ICAM-1 adhesion molecules on keratinocytes

T cells are recruited to the epidermis and dermis and result in direct lymphocyte-

mediated cytotoxicity and apoptosis

Granulysin (released by T cells)-induced intrinsic apoptosis.

 SJS/TEN:
Drug molecules combine with host peptides to form immunogenic compounds
Drug molecules trigger T cell receptors directly
Drug molecules alter “self” antigens activating T cells
Keratinocyte is the target of an immune response resulting in apoptosis
Genetic differences may result in enhanced T cell activation
Soluble cytotoxic proteins (i.e., granulysin) trigger apoptosis (not direct cell–cell

interaction).

SIGNALMENT/HISTORY

 Dogs and cats.

 CADR: no age or sex predispositions: Shetland sheepdog, dalmatian, Yorkshire

terrier, miniature poodle, miniature schnauzer, Australian shepherd, Old English

sheepdog, Scottish terrier, wire-haired fox terrier, and greyhound; doberman pin-

schers and miniature schnauzers (sulfonamides); miniature schnauzers (shampoo-

induced exfoliative erythroderma).

 EM and SJS/TEN: no age, breed, or sex predispositions.

 Some types of drug reactions appear to have a familial basis (e.g., rabies vaccine

reactions in dogs have been diagnosed in littermates).

CLINICAL FEATURES

 CADR:
Wide variety of clinical symptoms reported
Contact dermatitis (erythema, papular eruption, scaling) from topical medica-

tions

Pruritus (resulting in excoriation), erythroderma, exfoliative dermatitis,

urticaria, vasculitis most commonly described with systemic medications (Fig-

ure 17.8)

Drug-induced pemphigus/pemphigoid; can closely mimic the autoimmune

(spontaneous) forms of these diseases (Figures 17.9, 17.10)

Focal ischemic dermatopathy/vasculitis post vaccination (Figure 17.11)

Systemic symptoms (e.g., depression, anorexia, fever, lameness), hematologic

changes

Urticaria/angioedema: results from an immediate (type I) hypersensitivity;

requires prior sensitization; increased vascular permeability leads to fluid leak-

age into the interstitium (Figure 17.12)