Small Animal Dermatology, 3rd edition

274 DISEASES/DISORDERS

Hypersensitivity vasculitis: inflammation of cutaneous vasculature; results in

poor blood flow and anoxic injury to recipient tissue; in most cases, thought

to represent a type III hypersensitivity response

Exfoliative erythroderma: diffuse erythematous response caused by vasodilation;

often leads to exfoliation (diffuse scaling) and intense erythema

Superficial suppurative necrolytic dermatitis of miniature schnauzers: systemic

symptoms and painful ulcerative patches developing within 72 hours of bathing/

topical therapy.

 EM:
Classic “target” or “bull’s-eye” lesion not a common finding; seen as annular

lesions with erythematous, often scaling borders and central clearing; postin-

flammatory pigmentation centrally (Figure 17.13)

EM minor: no systemic symptoms; none or only one mucosal site involvement

EM major: systemic symptoms; more than one mucosal site involvement

Glabrous skin of ventrum, flanks, axillae, inguinal; pinnae; mucocutaneous

junctions

Some lesions may be significantly crusted (“old dog” EM) (Figure 17.14)

Macular and papular rashes often serpiginous and polycyclic: commonly accom-

pany pruritus as a nonspecific sign of inflammation (EM minor) (Figure 17.15)

Mucocutaneous ulceration/erosion, oral cavity, footpads, pinnae (EM major)

(Figures 17.16–17.18)

EM lesions may be plaque-like (palpable) or bullous

Spontaneous resolution possible (especially if the trigger is identified/treated/

removed).

 SJS/TEN:
Sudden onset
Systemic symptoms (e.g., depression, anorexia, fever)
Coalescing targetoid lesions lead to extensive necrosis and sloughing of

the epidermis in sheets; results in moist and intensely inflamed ulcerations

(Figures 17.19, 17.20)

Pseudo-Nikolsky sign (separation of epidermis by shearing force)

Generalized truncal lesions

Mucosal lesions common

Footpads often affected (Figure 17.21).

DIFFERENTIAL DIAGNOSIS

 Pruritus, macular/papular rashes, and urticaria/angioedema: allergic diseases (atopy,

food allergy, contact allergy) and reactions to ectoparasitism (scabies, flea bite allergy,

stinging insects), bacterial folliculitis, dermatophytosis.

 Exfoliative erythroderma with crusting: cutaneous T cell lymphoma, pemphigus/

pemphigoid, superficial necrolytic dermatitis, zinc-responsive dermatitis, seborrhea/

keratinization disorders.

 Vasculitis: infectious, neoplastic, and autoimmune diseases (especially lupus erythe-

matosus); many cases of vasculitis are idiopathic.