The term eosinophilic granuloma complex refers to a group of skin problems in cats caused by inflammation at the site and often initiated and exacerbated by the cat licking the area. The term is not a specific diagnosis but a description of the signs which occur in three different forms in the cat. These are eosinophilic ulcer, eosinophilic plaque and eosinophilic granuloma. Each form has its own pattern but all three are skin reactions to an underlying cause. The skin reaction may be a minor problem which disappears as mysteriously as it appeared and may never reappear. However, it can become a persistent problem causing a great deal of tissue damage and discomfort to the cat. Owners are often (understandably) distressed by the lesions and the cat's constant licking.

The rather clinical name actually describes the problem. Eosinophils are a type of white blood cell which are mobilised by the body's immune system to combat invasion at the site of infection or react to the presence of a foreign body. They will be sent to a particular spot of skin and inflammation will occur. If they do their job and leave, the inflammation will subside. However, occasionally they continue to work in the area for long periods and the inflammation can give rise to a lump which the cat may find itchy. These lumps may then develop into granulomas, types of skin lesion which look like raised sores.

Eosinophilic ulcer  

Also called an indolent or rodent ulcer, this can occur on the upper lip near a canine tooth and has raised edges and a pink/yellow surface. Although they look very sensitive, the lesions do not seem to be painful or itchy. The lesion may start off as a lump but can become ulcerated and can spread towards the nose if the cat licks repeatedly. Licking with the rough feline tongue can cause more damage than the reaction itself There is some evidence to suggest that this is an allergic response to fleas or other allergies. It may have a genetic component and can be very difficult to find a cause in many cases and may be classed as 'idiopathic' - meaning of no known cause

Eosinophilic plaque      

Eosinophilic plaque usually presents as a raised, ulcerated, tough and scaly lesion on the body, often located on the cat's stomach and inner thigh. The cat may have licked the area and caused more damage to the skin. This is often seen in younger cats (2 to 6 years old) and can be associated with an allergic reaction to fleas, food or environmental allergens.

Eosinophilic granuloma   

Eosinophilic granuloma is also referred to as collagenolytic or linear granuloma and affected areas have damage to the collagen (the fibrous structure of the skin which gives it strength and support). There does not seem to be any breed, age or sex bias and lesions may not be itchy.

Skin lesions may be single or in groups and found anywhere on the body but commonly along the middle of the forelegs and as a band of raised hairless lesions along the back of the thighs in a pattern associated with grooming.

Another form associated with the chin and lower lip is referred to as 'pouting' or 'button lip'. The nose, muzzle, ears and at the junction of the pads and the haired skin on the foot may also be affected. The foot pads may be ulcerated and swollen and there may be loss of pigment. The skin lesions are usually red, raised, hairless and have a grainy look. There may also be lesions in the mouth.

Causes may include hypersensitivity to flea bites, reaction to food and environmental allergens. In the USA, Australia, cats kept in an insect-free environment have improved rapidly.

Diagnosis  

Diagnosis will usually require the veterinary surgeon to take a skin sample, needle aspirate (cells withdrawn from the area with a needle) or, preferably, a biopsy to rule out other causes such as cancer, abscess, reaction to a foreign body or fungal infection. The tissue will have characteristic changes associated with eosinophilic granuloma complex.

Treatment  

Treatment depends on the extent of the problem and trying to ascertain the cause of the reaction using flea treatments and diet trial (or an elimination diet). While fleas may be relatively easy to treat, getting to the root of a food allergy can be difficult. Small single lesions which do not seem to bother the cat may be left to heal themselves. If disease is more extensive, the vet may prescribe antibiotics for three to six weeks. If this does not prove effective, glucocorticoids (steroids) may be given by injection or tablet and the dose reduced gradually. Cats are relatively tolerant to steroids and do not seem to suffer from the same side effects as dogs and humans. Antihistamines may also be considered but a reliance upon glucocorticoids is usually essential in chronic cases where an underlying cause can not be established or controlled. If the disease does not respond, then treatment may be given to try and suppress the immune system. Some lesions may be removed with surgery, cryosurgery, laser therapy or radiation therapy if these are available.

Other therapies include giving essential fatty acids (EFAs) using a combination of evening primrose oil and fish oil in capsule/oil spray formulations administered orally or via the food for 4 to 6 weeks to see if this has a beneficial effect.