Page 1448 - Clinical Small Animal Internal Medicine

1386 Section 12 Skin and Ear Diseases

VetBooks.ir

Figure 157.11 Lichenification – results from chronic trauma, often Figure 157.12 Alopecia – may arise from several causes that lead
due to friction. Lichenification is often accompanied by superficial to damage to hairs and/or hair follicles, or result from abnormal
bacterial folliculitis and/or Malassezia dermatitis. DDx – chronic hair growth. DDx – primary: endocrinopathies, follicular dysplasia,
and pruritic dermatopathies, intertrigo, and keratinization telogen effluvium, and anagen defluxion. Secondary: pruritus,
disorders. Photograph illustrates the abdomen and inguinal area superficial bacterial folliculitis, dermatophytosis, and demodicosis.
of a dog with chronic atopic dermatitis. Photograph illustrates multiple annular to coalescing areas of
alopecia in a beagle with alopecia areata.

Figure 157.14 Crust – forms when purulent exudate, serum,
blood, other dried exudates, or cells and/or scales adhere to the
Figure 157.13 Scale – results from increased production of skin surface. DDx – primary: SND, vitamin A‐responsive dermatitis,
keratinocytes, such as occurs with abnormalities of keratinization, zinc‐responsive dermatosis, primary idiopathic seborrhea.
inflammatory disorders or from increased retention of Secondary: pyoderma, dermatophytosis, pemphigus, and lupus.
corneocytes. DDx – primary: ichthyosis, primary idiopathic The coloration, thickness, and adherence of crusts can provide
seborrhea, various follicular dysplasias. Secondary: chronic insight as to the underlying disease process. Pyoderma can result
inflammation or any direct insult to the epidermis such as in brown‐dark red (indicating hemorrhage) or yellow‐green crusts.
epidermal infiltration of neoplastic lymphocytes in cutaneous Dark crusts indicate deeper tissue damage or hemorrhage as
T cell lymphoma. Photograph illustrates large, whitish‐gray sheets occurs with traumatic wounds, furunculosis, and vasculitis.
of scale in a golden retriever with ichthyosis. Honey‐colored crusts usually indicate an infection but also occur
with some autoimmune diseases, particularly pemphigus
foliaceus. Thick, dry yellowish crusts are more common with
scabies and zinc‐responsive dermatosis. Tightly adhered crusts are
more common in zinc‐responsive dermatosis, SND, pemphigus,
and some cases of seborrhea. Photograph illustrates the typical
honey‐colored crusts associated with pemphigus foliaceus.