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At a glance
About: Steatitis is a painful condition caused by inflammation and yellowing of the fat tissue.
Causes: It is caused by feeding a diet in unsaturated fatty acids and deficient in vitamin E, which acts as an antioxidant. When there is an overabundance of saturated fatty acids, damage occurs to the body fat, resulting in painful inflammation.
Symptoms: Solid masses under the skin, greasy coat, loss of appetite, reluctance to move, pain when touched and depression.
Treatment: Dietary changes, vitamin E supplements, corticosteroids and pain medication.
What is steatitis?
Steatitis (yellow fat disease, pansteatitis) is a painful condition characterised by a marked inflammation and yellow colouration of the adipose (fat) tissue. The discolouration of the fatty tissue is caused by deposits of large amounts of ceroid pigment and is caused by feeding a diet high in unsaturated fatty acids and deficient in vitamin E. Oily fish, especially red tuna, but also sardines and white fish are the most common cause of this condition.
Vitamin E acts as an antioxidant and found in foods; these antioxidants inhibit oxidation, which is a reaction that produces unstable chemicals known as free radicals which damage cells. Unfortunately, tuna is an inadequate source of Vitamin E. Therefore the overabundance of unsaturated fatty acids (which also oxidise and destroy Vitamin E), combined with the deficiency of vitamin E causes damage to body fat, which results in the painful inflammatory response. 
Other less common causes of steatitis include pancreatitis, infection, inflammatory disorders, vasculopathy, trauma, cancer, and immune-mediated diseases.
Steatitis can occur in cats of any age; however, it is more common in obese cats.
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. In some cases, your veterinarian will be able to diagnose steatitis based on symptoms and palpation of hard, painful nodules under the skin.
- Biochemical profile and complete blood count which may reveal an elevated white blood cell and neutrophil count
- Biopsy of the subcutaneous tissue. The sample will show a yellow/orange appearance and firm with a nodular appearance
- Elimination of fish from the diet immediately.
- Supplementation with Vitamin E.
- Nutritional support, such as tube feeding.
- Some veterinarians recommend the use of corticosteroids such as prednisolone to reduce inflammation, pain, and fever.
- Supportive care which will include fluids and painkillers, to keep your cat comfortable.
- In some cases, surgical excision of necrotic fat.
Cats who receive prompt medical care have a good prognosis. Complete recovery will take three to four weeks.
Can I feed my cat human-grade tuna?
The short answer is yes, but only feed as a special treat; it should not be a part of the cat’s ordinary diet.
Tuna can be addictive to cats, and they can quickly develop a taste for tuna and refuse any other foods. The term “tuna junkie” has been used to describe such cats.
Raw fish also contains the enzyme thiaminase which destroys thiamine (Vitamin B1), resulting in thiamine deficiency. Cooking destroys thiaminase, thus protecting thiamine.
What’s the difference between human-grade tuna and tuna flavoured cat food?
Human grade tuna is just that. Tuna flavoured cat food is not 100% tuna and usually contains other meats and nutrients which are necessary for the cat’s diet.
Limit the amount of fish flavoured cat food as hyperthyroidism has been linked to feeding tinned food, particularly fish flavours.
*1 The Cornell Book of Cats.