Page 1551 - Clinical Small Animal Internal Medicine

168 Cutaneous Manifestations of Systemic Disease 1489

present. Secondary Malassezia dermatitis and bacterial not helpful. Ultrasonography can be useful in finding the
VetBooks.ir overgrowth can occur. underlying neoplasm, but often fails to reveal a mass.
The pathogenesis of the cutaneous syndrome is not
Unfortunately, this disease carries a poor to grave prog-
well understood, but is thought to be a cell‐mediated
is common.
immunologic reaction secondary to the underlying thy- nosis as many tumors are not resectable and metastasis
moma. A mediastinal mass can be detected in most
patients by radiography or ultrasonography and fine nee- Nodular Dermatofibrosis
dle aspirates can be diagnostic. Surgical removal of the
thymoma induces regression of the skin lesions. Median Nodular dermatofibrosis is a syndrome of multiple cuta-
overall survival time after surgery in one small study was neous nodules of collagenous origin occurring in con-
1825 days, with a three‐year chance of survival of 74%. junction with renal cystadenocarcinomas or
cystadenomas in dogs. This syndrome most commonly
occurs in German shepherd dogs and their crosses, and
Feline Paraneoplastic Alopecia
the renal disease is almost always bilateral. The disease is
Feline paraneoplastic alopecia is a highly visually dis- typically diagnosed in middle age. In addition to the
tinct, bilaterally symmetric progressive alopecia in which renal tumors, intact females can develop uterine leiomy-
the skin appears unusually thin and shiny (Figure 168.9). omas. In the German shepherd dog, an autosomal domi-
The majority of affected patients are older cats with nant mode of inheritance is suspected. Molecular studies
pancreatic carcinoma, but the condition has also been have suggested that nodular dermatofibrosis is not a
reported with biliary carcinoma. The pathogenesis of the paraneoplastic syndrome but a genetic disease linked to
cutaneous lesions is poorly understood but is thought to a mutation in the gene encoding folliculin. It is analogous
be induced by the cytokine milieu released by the tumor. to Birt–Hogg–Dubé syndrome in humans. Rarely, nodu-
The alopecia typically begins on the ventral abdomen lar dermatofibrosis has been found in other breeds in the
and thorax, with progression to the head and medial absence of internal tumors.
extremities. The hair epilates easily, revealing smooth, Nodules are typically most numerous on the head and
shiny, glistening skin that is not fragile. Some affected limbs, including the feet, but can occur on other areas of
cats have scaly or fissured footpads that can be painful. the skin, generally in a symmetric fashion. They are firm,
The condition is not always pruritic but affected cats localized in the dermis or subcutaneous layer, mobile,
may groom excessively, especially if the skin disease is and covered by intact epidermis that can sometimes
complicated by secondary Malassezia dermatitis. The ulcerate, causing lameness. The nodules range in size but
onset is typically quite acute and rapidly progressive. can be up to 5 cm in some cases. The disease has a pro-
Affected cats are systemically ill and exhibit weight loss. tracted clinical course, with the appearance of renal fail-
The clinical appearance is visually striking and distinc- ure or metastasis occurring months or more often years
tive. Histopathology confirms the diagnosis. Routine from the time that the lesions are first noticed. The mean
hematology and serum biochemical profiles are typically time from first observation of nodular dermatofibrosis
to death is about 2.5 years.
The diagnosis of nodular dermatofibrosis is generally
made by histopathology of the skin masses combined with
abdominal ultrasonography. When skin biopsies are col-
lected, the presence of multiple lesions and the suspicion
of this condition should be conveyed to the pathologist.
There are currently no reported effective treatment
options and because bilateral renal disease is virtually
always present, surgery is not an option. The cutaneous
nodules should be monitored and excised if they become
ulcerated or infected leading to patient discomfort or if
they disturb patient mobility due to their size or location.
It is important to relay the fairly slow progression of the
disease to owners of affected dogs.

Feline “Lung‐Digit” Syndrome

Figure 168.9 Feline paraneoplastic alopecia in an adult cat with Feline “lung‐digit syndrome” describes an unusual
pancreatic carcinoma. Source: Courtesy of Dr Edward Clark. pattern of metastasis that is seen with various types of