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Scottish Terriers
Recently, Scottish terriers with a benign diffuse vacuolar hepatopathy have been described [3]. The suggested term is idiopathic vacuolar hepatopathy. Although the lesion appears typical for “steroid hepatopathy” with glycogen accumulation, clinical findings or laboratory evidence of Cushing’s disease are absent. Rarely, some dogs may be polydipsic and polyuria. Physical examination is unremarkable. Laboratory findings include marked elevations of ALP (predominantly the corticosteroid-induced isoenzyme) with normal GGT, ALT, AST, and bilirubin). Serum bile acid concentrations are normal or mildly increased. Adrenal glands are normal size on ultrasound. Further evaluation of other adrenal steroids such as progesterone, estradiol, DHEAS-S or 17-hydroxyprogesterone revealed that most affected dogs have increases in 17-hydroxyprogesterone or progesterone. These hormones could cause glycogen accumulation in the liver [3].
Most affected dogs can live out their lives without clinical significance to the increased enzymes and vacuolar change. However, some dogs become polydipsic and polyuric; rarely, signs of overt Cushing’s disease develop. Treatment with ketoconazole or Lysodren® as for Cushing’s disease will decrease the ALP, supporting an adrenal mechanism for the vacuolar change and increased ALP activity. Trilostane (Modrenal®), a competitive inhibitor of the enzyme 3β-hydroxysteroid dehydrogenase that converts pregnenolone to progesterone, may be a safer therapy but the drug is currently unavailable in the US. Consequently, adrenolytic treatment is not currently recommended for this benign disorder [3].
Hepatoprotective therapy with antioxidants or S-adenosylmethionine may be helpful but have not been studied in this disorder.
The cause of idiopathic vacuolar hepatopathy in Scottish terriers is currently unknown. Potential mechanisms could include pituitary or adrenal hyperplasia producing aberrant steroids or a deficiency in an enzyme pathway in adrenal metabolism of steroids [3]. Healthy Scottish terriers have also been shown to have higher ALP activity than other breeds of dogs [21]. A benign asymptomatic hyperphosphatemia has been proposed [22].