Page 1447 - Clinical Small Animal Internal Medicine

157 Approach to the Patient with Dermatologic Disease 1385

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Figure 157.7 Epidermal collarette – these are formed from the
remnants of a pustule or vesicle after the roof has been lost, or
caused by a point source of inflammation, as seen with papules.
DDx – superficial bacterial folliculitis most commonly. Fungal
infection, immune‐mediated dermatoses, contact hypersensitivity,
and insect bite reaction are less common causes. Photograph
illustrates an epidermal collarette associated with superficial
bacterial folliculitis.
Figure 157.9 Erosion/ulceration – develop due to rapid death
and/or loss of keratinocytes as a consequence of self‐inflicted
trauma or inflammation. An ulcer denotes a deep pathologic
process. DDx – autoimmune dermatoses, erythema multiforme,
toxic epidermal necrolysis, drug reaction, SND, feline indolent
ulcer, deep pyoderma, deep mycoses, vasculitis, neoplasia,
chemical/thermal burn. Photograph illustrates an ulcer on the
lateral aspect of the thorax of a dog with a cutaneous adverse
drug reaction secondary to itraconazole therapy.

Figure 157.8 Excoriation – these lesions are self‐induced and
occur secondary to scratching, biting, and/or rubbing. Usually
result from pruritus. Photograph illustrates excoriations and
erosions due to scratching and licking on the lateral aspect of the
thorax of a cat with adverse food reaction.

therapeutic trials, biopsy and histopathology, and tests
of noncutaneous organs.
Figure 157.10 Fissure – lesions may be caused by underlying
disease or injury when the skin is thick and then subjected to
Screening Tests sudden swelling. DDx – SND, canine distemper, zinc‐responsive
Cytology dermatosis, chronic skin diseases, and keratinization disorders.
Cytology is a powerful tool, allowing one to quickly deter- Photograph illustrates fissures on the metacarpal pawpad of a
dog with SND.
mine whether a lesion is sterile or if infectious organisms
and inflammation are present. It allows the clinician to pre-
sumptively diagnose a patient with autoimmune diseases, cutaneous lymphoma and mast cell tumors. Cytology can
such as pemphigus, when acantholytic cells are observed. be performed in a number of ways depending on the area
Neoplastic processes may also be identified, such as and the condition of the skin being sampled.