Page 1446 - Clinical Small Animal Internal Medicine

1384 Section 12 Skin and Ear Diseases

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Figure 157.3 Vesicle – lesions are fragile, transient, and difficult to Figure 157.5 Wheal (hive) – these edematous lesions typically
find given that they develop secondary to inflammation and loss disappear within minutes to hours. When larger regional areas are
of cutaneous cellular and structural cohesion. DDx – viral involved such as the muzzle or eyelids, this is called angioedema.
infections, irritants, drug reactions, and autoimmune diseases DDx – vaccine, drug and insect bite reactions, and hypersensitivity
including pemphigus vulgaris, lupus, and subepidermal blistering disorders. Photograph illustrates urticaria on the abdomen of a
diseases such as mucous membrane pemphigoid, and dog.
epidermolysis bullosa acquisita. Photograph illustrates vesicles on
the lower lip margin in a dog with epidermolysis bullosa acquisita.
Source: Courtesy of Sandra Koch.

Figure 157.4 Pustule – lesions arise due to neutrophilic
inflammation, occasionally eosinophilic. DDx – superficial Figure 157.6 Nodule – these lesions develop due to an
bacterial folliculitis, impetigo, dermatophytosis, demodicosis, inflammatory or neoplastic cellular infiltrate, or from deposition of
pemphigus foliaceus, lupus, and subcorneal pustular dermatosis. metabolic products such as fibrin and crystalline material
If eosinophils predominate, consider sterile eosinophilic extending to the dermis and subcutis. There are numerous
pustulosis, insect or contact hypersensitivity and ectoparasites. neoplastic and nonneoplastic causes. Nonneoplastic causes
Photograph illustrates pustules associated with superficial include infectious and noninfectious etiologies. DDx – infectious
bacterial folliculitis. causes: bacterial infections such as actinomycosis, nocardiosis,
feline leprosy, canine leproid granuloma, atypical mycobacteriosis,
and bacterial furunculosis. Fungal causes include blastomycosis,
and/or confirm a specific diagnosis. There are four cryptococcosis, coccidioidomycosis, sporotrichosis,
basic screening tests that every clinician should be histoplasmosis, dermatophytic kerion, aspergillosis,
phaeohyphomycosis, hyalohyphomycosis, pythiosis, and
adept at and perform often, as they are easy, rapid, and lagenidiosis. Algal causes include protothecosis. Parasitic and
inexpensive to conduct and yield immediate results. protozoal causes include leishmaniasis, dracunculiasis, Cuterebra,
This minimum database generally includes cytology, and Neospora. Noninfectious causes: calcinosis cutis, xanthomas,
including various techniques of cutaneous cytology sterile nodular panniculitis, sterile granulomatous
and otic cytology, as well as trichography, skin scrapes, pyogranulomatous syndrome, cutaneous reactive histiocytosis,
juvenile cellulitis, foreign body reaction, and eosinophilic
and cultures. Other diagnostic tests of importance to granuloma. Photograph illustrates multiple nodules on the muzzle
the dermatologic patient that will be discussed include of a dog with sterile granulomatous pyogranulomatous syndrome.