Eosinophilic Granuloma Complex in Cats

Overview of Feline Eosinophilic Granuloma Complex 

The term eosinophilic granuloma complex (EGC) refers to a group of skin lesions that represent an allergic reaction in the cat’s skin. These occur in three forms, and your cat may have any or all of them. These forms include:

  • Eosinophilic granulomas. These nodules are raised, yellow or pink in color, and usually are not itchy. They occur on the back of the rear legs, in and around the mouth and on the face and are most common in adolescent kittens.
  • Eosinophilic plaque. These patches look like a raised, round red lesions that may be ulcerated. They are usually itchy and are most commonly found on the belly, inner thigh or throat.
  • Indolent ulcer. Erosions on the margin of the upper lip and sometimes on the tongue are red in color and glistening in appearance. They may be painful and may affect the cat’s willingness to eat.

    On microscopic examination of skin biopsy specimens, all of these forms of the disease are characterized by accumulation of large numbers of eosinophils, a type of white blood cell found in allergic and parasitic inflammatory disorders.

    A common cause is thought to be flea allergy, but atopy, a form of allergy triggered by inhaled environmental allergens such as pollens and dust, and food allergies also can cause EGC lesions in cats. An allergic response to mosquitoes is also suspected.

    Female cats may be more likely to be affected than male cats, but only rarely is it found in dogs, such as Siberian huskies.

    Diagnosis of Eosinophilic Granuloma Complex in Cats

    Diagnostic tests may be needed to diagnose eosinophilic granuloma complex and assess the extent of the disorder and its effects on the cat. Often, a presumptive diagnosis is made based on the clinical appearance of the lesions and their response to treatment. Tests may include:

  • A complete medical history and physical examination. Physical examination is very important because of the distinctive clinical appearance of the lesions.
  • A complete blood count (CBC or hemogram) to evaluate for anemia, infection, inflammation and circulating eosinophils
  • Skin biopsy to rule out other causes of lesions with a similar appearance – most notably skin cancers such as squamous cell carcinoma or cutaneous lymphosarcoma. The results of the skin biopsy will confirm the diagnosis of eosinophilic granuloma complex.
  • Treatment of Eosinophilic Granuloma Complex in Cats

    Treatment for eosinophilic granuloma complex may include one or more of the following:

  • Corticosteroids. Cortisone-like drugs are used most commonly to treat cats with suspected eosinophilic granuloma complex. Unlike other feline skin reactions such as miliary dermatitis, the lesions of eosinophilic granuloma complex rarely respond to removal of the allergen alone. The anti-inflammatory effects of corticosteroid drugs such as prednisone and methylprednisolone acetate are usually needed.
  • Flea control, elimination diets to identify food allergens, and treatment for inhaled allergens (those that cause atopy) may help prevent recurrence.
  • Home Care and Prevention

    At home, administer as directed all medications prescribed by your veterinarian, and contact your veterinarian if you are having difficulty medicating your pet or if the condition has worsened.

    Follow-up appointments are very important because the lesions of eosinophilic granuloma complex often require more than one treatment for complete success.

    Preventative measures include flea control, elimination diets to identify food allergens and treatment for inhaled allergens.

    In-depth Information on Eosinophilic Granuloma Complex in Cats

    Eosinophilic granuloma complex refers to a characteristic allergic skin reaction in cats. Flea allergy is thought to be the most common cause of this type of allergic skin reaction. Allergic reactions to food components, which are allergens that are inhaled into the respiratory system (atopy), and allergic reactions to other insects such as mosquitoes also can result in eosinophilic skin lesions. In unusual cases, an allergic cause cannot be found and a hereditary disorder is suspected.

    Eosinophilic plaques usually are found on the abdomen or the inner thighs. They are raised, red lesions that may be glistening in appearance or oozing serum. Eosinophilic plaque lesions are extremely itchy (pruritic) and often are surrounded by broken hairs from constant licking of the area by the cat with its barbed tongue. Other skin diseases that can produce similar lesions include bacterial or fungal infections and some types of skin cancer including mast cell tumors and cutaneous forms of lymphosarcoma.

    Eosinophilic granulomas often are found on the backs of the legs, on the roof of the mouth or on the tongue, and on the lower lip causing the cat to have a pouting expression. Lesions on the back of the legs usually are raised, round, and pink or yellow in color. More than one lesion may be present and they tend to occur in a linear distribution along the leg. As with eosinophilic plaques, bacterial and fungal infections and certain types of skin cancer such as mast cell tumor and cutaneous lymphosarcoma can have a similar appearance.

    Indolent ulcers, also called rodent ulcers almost always are found on the upper lip and usually are confined to one side. Occasionally, they may be found on both sides of the lip or inside of the mouth. The lesions most often are raised and ulcerated, causing a dramatic change in the appearance of the lip. Indolent ulcers may represent a precancerous lesion and, if untreated, eventually may develop into a malignant skin tumor called squamous cell carcinoma. Once again, bacterial and fungal infections and skin tumors (including mast cell tumor, cutaneous lymphosarcoma and squamous cell carcinoma) are diseases that may result in a similar appearance.

    In some cats, more than one type of eosinophilic skin disease can occur simultaneously.

    Diagnosis In-depth

    Diagnostic tests may be performed to identify underlying diseases, especially certain types of skin cancer) that may be confused with eosinophilic granuloma complex. Your veterinarian may recommend the following:

  • History and physical. The lesions of eosinophilic granuloma complex usually are identified based on their characteristic appearance. Your veterinarian will take a thorough medical history and perform a complete physical examination. The history will be directed toward identification of potential allergens that may have resulted in eosinophilic granuloma complex. Careful grooming of the hair coat with a flea comb may be performed to identify fleas. During this procedure, a fine-toothed comb is passed through the cat’s hair coat. The space between the teeth of the comb is small enough so that fleas are trapped and removed from the hair. The presence of broken or “barbered” hairs indicate that the cat is repeatedly licking the affected area and indicates that the problem is itchy.
  • Skin biopsy. Biopsy of eosinophilic granulomas and eosinophilic plaques show dermatitis with many eosinophils in the lesion. Eosinophils are a type of inflammatory cell that accumulate in lesions caused by allergens or parasites. Biopsy is less helpful in cats with indolent ulcers because eosinophils are often absent by the time the lesion is clinically apparent. Biopsy is most valuable to rule out other causes of similar lesions especially bacterial and fungal infections and certain types of skin cancer including mast cell tumor, cutaneous lymphosarcoma and squamous cell carcinoma.
  • Culture. Bacterial or fungal culture of lesions may be performed to identify bacterial or fungal infection.
  • A complete blood count (CBC). This test often shows increased numbers of circulating eosinophils in cats with eosinophilic plaques, sometimes in cats with eosinophilic granulomas, and rarely in those with indolent ulcers.
  • Strict flea control. Flea control should be maintained on the animal and in his environment to rule out flea allergy as the underlying cause of eosinophilic granuloma complex. Although the lesions may not resolve completely with flea treatment alone, lesions would not be expected to recur after successful treatment if fleas have been simultaneously eradicated.
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    Treatment In-depth

  • A food trial. Placing the cat on a hypoallergenic diet for a period of time may be utilized to assess the role of food allergens in some cats with eosinophilic granuloma complex.
  • Specific tests. Skin testing to identify offending inhaled allergens or specific blood tests for allergy may be recommended to evaluate some affected cats for atopy.

    Optimal therapy of any serious or persistent medical condition depends on establishing the correct diagnosis. Eosinophilic granuloma complex occurs in several forms and may have several potential underlying causes. If possible, the underlying cause should be identified before specific treatment is recommended. Medication with anti-inflammatory drugs likely will be recommended for affected cats. Your veterinarian will determine if treatment is warranted, and if so which specific medication is indicated.

  • Treatment is usually aimed at suppressing the inflammatory response to the allergic stimulus. Corticosteroids often are used for this purpose. Short-acting oral corticosteroids like prednisone may be safer than long-acting injectable steroids like methylprednisolone acetate, but often the injectable form is used because it is more convenient in that the owner does not have to administer pills repeatedly to the cat. It is also effective as there are a few injections of corticosteroid that often cause the lesions to regress with minimal or no adverse effects.

    Methylprednisolone acetate is given every two weeks until lesions are healed. Adverse effects of corticosteroids can occur in cats but are less common and less severe than observed in dogs. Identification and treatment of underlying allergic conditions may be necessary to prevent recurrence of the eosinophilic granuloma complex lesions. Other drugs that suppress eosinophil function may be necessary if corticosteroids are not effective or cannot be tolerated.

  • Antibiotics may be required to treat lesions that do not respond to steroid therapy alone, especially when secondary bacterial infection is suspected. Indolent ulcers in particular may be helped by antibiotic treatment.
  • Fatty acid supplements may be helpful and may decrease the amount of steroids needed.
  • Progesterone-like hormonal drugs such as megestrol acetate often are effective, but adverse effects are relatively common and can be severe. These may include uterine infection and mammary tumors. Therefore, these drugs currently are not recommended to treat eosinophilic granuloma complex.
  • Treatment for fleas is essential and should be performed in all cats, regardless of whether or not fleas actually are seen. Flea allergic cats can be very good at removing fleas by grooming themselves, and fleas and flea dirt are uncommonly seen. Flea medications that kill adult fleas before they can bite are required for adequate protection.
  • Allergy injections based on skin allergy testing (hyposensitization) may be recommended in cats that have recurrent eosinophilic skin lesions that do not respond to flea control.
  • A food trial may be needed to identify an underlying food allergy. During the trial, the cat must be fed a diet that contains only ingredients to which the cat has not been previously exposed.
  • Home Care 

    Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow–up can be crucial, especially if your cat does not improve as expected. Administer as directed all medications prescribed by your veterinarian. Therapy must be continued until lesions have completely resolved. Alert your veterinarian if you are having difficulty treating your pet.

    Recheck appointments are important to the long-term success of treatment. A diagnostic evaluation for underlying allergic disease like atopy or food allergy may be necessary if lesions recur.

    Continue a complete flea control program as prescribed by your veterinarian even after the skin lesions have healed, especially in outdoor cats. Observe your cat’s skin and mouth closely. Lesions are more easily treated if treatment is begun early in the disease process.

    As most of these cases are related to allergies, especially flea allergy, aggressive flea control is recommended to prevent the occurrence of a granuloma. Other allergies cannot be avoided.

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