Yellow fat disease is characterized by a marked inflammation of adipose tissue and deposition of “ceroid” pigment in fat cells. It may be seen alone in cats or with accompanying myopathy in rats, mink, foals, and pigs.
It is believed that an overabundance of unsaturated fatty acids in the ration, together with a deficiency of vitamin E or other antioxidants, results in lipid peroxidation and deposition of “ceroid” pigment in the adipose tissue. Most naturally occurring and experimentally induced cases have been in animals that have had fish or fish by-products as all or part of the diet. The specific cause is believed to be related jointly to the high unsaturation of the fish oil fatty acids and their lack of protection with vitamin E or other antioxidants.
Affected cats are frequently obese, usually young, and of either sex. They lose agility, are unwilling to move, and resent palpation of the back or abdomen. In advanced disease, even a light touch causes pain. Fever is a constant finding, and anorexia may be present.
In mink, kits may be affected with steatitis shortly after weaning and, if untreated, losses may continue until pelting time. Signs appear suddenly; the kits may refuse a night feeding and be dead by morning. Affected mink may refuse their feed and show a peculiar, unsteady hop, followed by complete impairment of locomotion and coma. At pelting, survivors show yellow fat deposits and hemoglobinuria.
The typical laboratory finding is an increased WBC count, with neutrophilia and sometimes eosinophilia. Biopsy of the subcutaneous fat shows it to be yellowish brown and firm. Histologic examination reveals severe inflammatory changes and associated ceroid pigment.
The offending excessive fat source must be removed from the diet. Administration of vitamin E, in the form of alpha-tocopherol, at least 30 mg daily for cats, or 15 mg daily for mink, is necessary. Antibiotics are of doubtful value, despite the fever and leukocytosis. Parenteral use of fluids is not advisable unless dehydration exists. Because of associated pain, affected animals should be handled as little as possible.