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168 Cutaneous Manifestations of Systemic Disease 1485

appear simultaneously or sequentially. The classic but The ideal diagnostic method for systemic or localized
VetBooks.ir uncommon cutaneous manifestation of canine distem- mycoses is identification of the fungal organism by
cytologic and histopathologic examination of affected
per is “hard pad disease” – footpad and nasal hyperkera-
tosis. The footpads are thickened, fissured, and unusually
test for cryptococcosis and can also be used to monitor
hard. The centers of the footpads can feel surprisingly tissues. Serology is useful as a noninvasive diagnostic
hard even when they appear minimally affected. response to therapy. A sensitive urine or serum antigen
Widespread impetigo can also be seen in puppies. test is currently available for the diagnosis of blastomy-
The diagnosis is often made on the basis of clinical cosis when organisms are not found on cytology
signs in a dog with an inadequate vaccination history. or histopathology. Sampling of the affected tissue for
Histopathology and immunohistochemistry on affected a definitive mycotic rhinitis typically requires
skin can also be useful to confirm the diagnosis. rhinoscopy.

Systemic Mycoses Leishmaniasis
Cutaneous lesions consisting of papules, nodules, ulcers, Leishmania organisms are protozoa of several species
abscesses, and draining tracts are seen in many systemic that cause a spectrum of clinical disease in dogs and
mycoses. They are seen most commonly in blastomyco- other mammals, including cats. Leishmaniasis varies in
sis (20–50% of cases) and feline cryptococcosis (40%), its clinical presentation from focal to generalized
and result from hematogenous spread of the fungus to cutaneous disease to disseminated internal disease. The
the skin. Sporotrichosis is generally transmitted by severity varies from asymptomatic to fatal. Leishmania
cutaneous inoculation of fungal spores, in most cases protozoa are usually vector borne by sandflies, but verti-
resulting in cutaneous or cutaneous lymphatic signs. cal transmission and direct horizontal transmission are
However, cats with sporotrichosis have a high frequency likely important in certain populations of dogs.
of upper respiratory and lung lesions, suggesting that the Leishmaniasis has a worldwide distribution but is
inhalatory mode of infection also plays a role in this spe- endemic in parts of Europe (most commonly in the
cies, and the hematogenous route is important in the Mediterranean basin) and South and Central America. It
cutaneous dissemination of the disease. was considered to be of minimal importance in North
Nasal mycotic rhinitis in dogs (most commonly asper- America until the early 2000s, when Leishmania was
gillosis) is usually associated with profuse mucopurulent found in multiple foxhound kennels.
nasal discharge and can cause crusting and ulceration of Leishmaniasis in dogs most frequently combines
the nasal planum (Figure 168.6). Depigmentation of the cutaneous and internal disease. The most common sign
nasal planum ventral to the nares is a characteristic is a nonpruritic exfoliative dermatitis with alopecia
finding. that is generalized but most pronounced on the head
(Figure 168.7). A characteristic feature is adherent sil-
very‐white scale. Mucocutaneous ulcerations, alopecia,
and erythema can also be seen. Less commonly, nodular
skin disease is present.
The diagnosis of leishmaniasis can be made by cytol-
ogy (from skin, lymph nodes, bone marrow aspirates),
histopathology, PCR testing of blood and other tissues,
and antibody serology testing.

Lagenidiosis

Lagenidiosis is a rare disease caused by a fungus‐like,
aquatic, “water mold” oomycete of the genus Lagenidia.
It occurs most often in dogs living in the southeastern
United States and has been reported in cats. The disease
is sometimes limited to the skin and local lymph nodes,
but often also causes lesions at distant sites, including the
great blood vessels, respiratory tract, and mediastinum.
The systemic form is universally fatal. The diagnosis is
Figure 168.6 Mild nasal mycotic rhinitis in a mature dog with made by histopathology, which is similar to histopathol-
nasal aspergillosis. ogy from tissues originating from dogs with pythiosis or