Metabolic Diseases

3. Metabolic Diseases

Metabolic Epidermal Necrosis/Necrolytic Migratory Erythema

Necrolytic migratory erythema is a skin disease in humans, that most commonly occurs secondary to a glucagon-secreting pancreatic tumor (Tierney & Badger, 2004). However, liver disease, internal malignancies other than pancreatic tumors and even glucocorticoid administration have been reported as causes of this disease (Mullans & Cohen, 1998; Tierney & Badger, 2004).

In the dog and cat, the terms diabetic dermatopathy, hepatocutaneous syndrome, metabolic epidermal necrosis or superficial necrolytic dermatitis have all been used, but a standard nomenclature has not been accepted (Scott et al., 2001). In the dog, the most common causes are liver disease, hyperadrenocorticism, diabetes mellitus, pancreatic tumors and phenobarbital administration (Gross et al., 1993; March et al., 2004; Torres et al., 1997; Yoshida et al., 1996). Two of the four cats reported in the literature had hepatopathies and the remaining two had pancreatic tumors (Beardi, 2003; Godfrey & Rest, 2000; Kimmel et al., 2003; Patel et al., 1996). The exact pathogenesis of metabolic epidermal necrosis has not been elucidated, but a deficiency of amino acids, fatty acids and/or zinc is discussed in the dog (Outerbridge et al., 2002; Tierney & Badger, 2004).

Clinical signs in the cat include stomatitis, gingivitis, alopecia, scaling and mild crusting. The skin lesions are bilaterally symmetrical and affect the axillae, ventrum, and inguinal area as well as the tail. Foot pads and mucocutaneous junctions were affected in one cat. Skin biopsies show diagnostic features of severe parakeratosis with underlying severe edema of the upper epidermis, and irregular epidermal hyperplasia with mild to moderate inflammation of the underlying dermis and appendages. Ultrasonography of the liver may reveal a diffusely coarse echotexture with a reticular pattern or a pancreatic mass.

Treatment of human necrolytic migratory erythema involves removal of the pancreatic tumor, skin lesions subsequently resolve without further therapy (Chastain, 2001; Zhang et al., 2004). In dogs, removal of a pancreatic tumor has also resulted in complete clinical remission (Torres et al., 1997). However, in most patients, advanced liver disease is the cause. In these patients, high quality proteins such as eggs in association with zinc and fatty acid supplementation may be helpful. In severe cases, intravenous amino acid infusion may lead to temporary remission (Gross et al., 1993, Outerbridge et al., 2002). However, if the underlying disease cannot be treated successfully, the prognosis is poor. To date, successful treatment of this disease in the cat has not been reported.

Xanthoma

Feline xanthomas are benign granulomatous lesions with several possible causes (Table 9). Hereditary hyperlipoproteinemia is one possible etiology (Grieshaber, 1991; Johnstone et al., 1990; Jones et al., 1986). It may be due to congenital deficiency of lipoprotein lipase, an enzyme responsible for hydrolysis of the lipids in the chylomicrons and the release of free fatty acids in the peripheral tissues (Bauer & Verlander, 1984). Xanthomas have also been reported in cats with diabetes mellitus (Jones et al., 1986; Kwochka & Short, 1984). A case series of 5 cats described frequent high fat treats such as cream, butter and ice cream as possible causes, all of these cats responded to a low fat diet (Vitale et al., 1998). Leakage with extraand intracellular deposition of lipoproteins from the capillaries into the tissue is suspected to occur in humans and may also occur in cats. Idiopathic feline xanthoma may also exist (Denerolle, 1992).

Lesions most commonly develop on the head, particularly the preauricular area and pinnae (Figure 11). Bony prominences may also be affected.

Figure 11. Lesions due to a specific underlying cause resolve spontaneously once the underlying cause is addressed successfully. A low-fat diet is recommended and will be particularly useful in cats with the idiopathic form of xanthoma. (©R. Mueller & ©V. Biourge).

The diagnosis is confirmed histologically. A nodular to diffuse granulomatous inflammation with foamy macrophages and multinucleated giant cells is characteristic. Diabetes mellitus or excess dietary fat intake should be ruled out as underlying causes.

Treatment consists of addressing the underlying disease and feeding a low fat diet (< 25 % of calories of the diet provided by fat). If diabetes mellitus is treated successfully, the diet may be changed back to normal. In patients with idiopathic or congenital xanthomas, it may be prudent to continue the low-fat diet for the remainder of the pets life.

Lesions due to a specific underlying cause resolve spontaneously once the underlying cause is addressed successfully. A low-fat diet is recommended and will be particularly useful in cats with the idiopathic form of xanthoma.