Contributors: Rosanna Marsella, Ian Mason, David Scarff, David Godfrey

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Cause: skin disease due to an allergic reaction to environmental allergens.
  • Signs: variable including symmetrical alopecia, miliary dermatitis, eosinophilic plaques and pruritus of head and neck.
  • Diagnosis: elimination of other causes of pruritus; history and clinical signs. Allergy testing is used to identify individual offending allergens.
  • Prognosis: control likely but life-long treatment required.

Presenting Signs

  • Pruritus.
  • Symmetrical alopecia  Ventral alopecia - hyperadrenocorticism .
  • Miliary dermatitis  Skin: miliary dermatitis - DSH 8 years .
  • Pruritus affecting the head and neck.
  • Eosinophilic granuloma complex lesions  Skin: eosinophilic granuloma - mouth  Skin: eosinophilic ulcer on mouth - DSH .
  • Chronically relapsing dermatitis.
  • Excessive licking/grooming although this may not have been noticed by the owner.
  • May be markedly seasonal.

Geographic Incidence

  • Atopy is universally recognized, considered to be the second most common dermatological hypersensitivity in the cat.

Breed Predisposition

  • There is some evidence of breed predisposition for the DSH, Abyssinian Abyssinian and Devon Rex Devon Rex.

Cost Considerations

  • The diagnostic protocol can be lengthy and expensive.
  • Needs life-long management regimes which may be costly.
  • In cats with seasonal pruritus, inexpensive treatment will often control the problem.

Pathogenesis

Predisposing Factors

General

  • Familial history of atopy is assumed from the condition in other species but this will rarely be helpful in clinically assessing a feline patient.

Pathophysiology

  • Feline atopy is caused by an exaggerated or inappropriate immune response of the affected cat to environmental allergens.
  • The pathogenesis of this inappropriate response is unknown, although it is believed that a reaginic antibody (IgE and probably IgG) is present in the skin.
  • The reaginic antibody is assumed to cause an immediate reaction to the intradermal injection of antigens.
  • The precise immunology and pathogenesis remain obscure. Feline IgE has been ideintified and cloned but whether it is important in all cases that are currently considered to have feline atopic dermatitis is not clear. For example, many of these cases will be negative on both intradermal and serological allergy testing (which should be detecting allergen-specific IgE) and significant numbers that do have positive results on these tests fail to have a good response to allergen specific immunotherapy Allergy-specific immunotherapy based on them.

Diagnosis

Presenting Problems

  • Pruritus (there may be only indirect evidence of this and trichography of short hairs is very helpful to establish that self-trauma has occurred).
  • Symmetrical alopecia - due to over grooming.
  • Milliary dermatitis Dermatitis: miliary.
  • Eosinophilic granuloma complex lesions.
  • Secondary skin lesions due to self trauma.
  • Perhaps 20% of cats with the signs listed above will have a diagnosis of atopic dermatitis made after a complete dermatologic diagnostic investigation.

Client History

  • Pruritus.

Clinical Signs

  • Evidence of self trauma - excoriation, broken hair shafts (barbering).
  • Non-inflammatory symmetrical alopecia  Skin: atopy and food allergy - acute   Skin: atopy - Persian 2 years .
  • Eosinophilic granuloma complex lesions  Skin: eosinophilic granuloma - mouth   Skin: eosinophilic ulcer on mouth - DSH .
  • Miliary dermatitis  Skin: miliary dermatitis - DSH 8 years .
  • Initially non-lesional pruritus, especially affecting head and neck.
  • Lymphadenopathy Lymphadenopathy in chronic cases especially if miliary dermatitis, excoriation or eosinophilic plaques present.
  • Self-trauma to face and feet.
  • Ceruminous pruritic otitis externa.
  • Sneezing  Sneezing .
  • Chronic coughing.

Diagnostic Investigation

  • Investigation rests largely on ruling out the main differentials.
  • Allergy testing is used largely to aid treatment with allergen specific immunotherapy rather than being part of the diagnosis of atopic dermatitis. This can be done using intradermal skin testing   Intradermal skin test or serology.  Because false positives and negatives are common using both techniques some clinicians routinely use both techniques for each patient.
  • It is important to establish whether secondary pyoderma is present in each case.

Differential Diagnosis

Treatment

Standard Treatment

  • Avoidance, hyposensitization and antipruritic drugs.
  • Prednisolone Prednisolone 1-2 mg/kg SID-BID or methylprednisolone Methylprednisolone  0.8-1.6 mg SID-BID.
  • Parenteral glucocorticoids Therapeutics: glucocorticoids are effective in controlling pruritus in many atopic cats.
    Requires long-term medication so there is a risk of significant side-effects, especially increasing the risk of diabetes mellitus Diabetes mellitus.Long-term therapy is likely safer using low dose, alternate day therapy.
  • Dexamethasone Dexamethasone (longer acting formulations) or methylprednisolone acetate 5 mg/kg IM can be used with caution in cats which are impossible to dose orally and seem to work in some cats that fail to respond to other steroids.
  • Higher doses of steroids are more likely to be required with eosinophilic granuloma complex disease or head and neck pruritus cases.
  • Treat any concurrent hypersensitivities (flea allergic dermatitis Flea bite hypersensitivity, food sensitivity Food hypersensitivity) to reduce the pruritic threshold and the need for additional treatment.
  • Allergen avoidance Skin: atopy - allergen avoidance has a small part to play in management. Need accurate identification of allergens by allergy skin testing. Most cats have multiple allergies making avoidance impossible.
  • Immunotherapy (hyposensitisation) is recommended where allergen avoidance is impossible, where signs are present for more than 4-6 months of the year and where antipruritic medication is ineffective or causes side effects. Success rates are poorly investigated but are probably broadly in line with the successes in atopic dogs, at around 2/3 patients being significantly helped.
  • Antihistamines are variably effective. Several may need to be tried in an individual. They are more effective in preventing pruritus than in initially bringing it under control. Chlorpheniramine maleate (unlicensed), 0.4 mg/kg PO BID-TID, is the most commonly recommended antihistamine  Chlorphenamine.
    Cats can be very sensitive to side effects of antihistamines.
  • Concurrent pyoderma should be treated. Cytology should be used to establish whether bacteria are present and antibiotics should be chosen based on sensitivities of suitable products.
  • SecondaryMalassezia overgrowth identified by, eg cytology should also be treated with itraconazole Itraconazole 5 mg/kg daily, reducing as possible, but this may need to be continued until the underlying hypersensitivity is controlled.
  • Ciclosporin Ciclosporin (Atopica) may be very useful in cats that require a long-term symptomatic intervention but do not respond well to glucocorticoids or that have side effects. There is some evidence that it is more effective than systemic steroids. It is an expensive treatment but is generally well tolerated. Knowing the cat's Toxoplasma status (IgG and IgM titers) may be useful prior to starting treatment. Toxoplasmosis Toxoplasmosis may be induced if the cat catches the parasite for the first time when on ciclosporin or if immunosuppression allows recrudescence. Knowing baseline titers will aid interpretation of Toxoplasma titers in cats that become ill during treatment.
  • Essential fatty acid supplementation Omega-3 fatty acids or enriched foods may be helpful, especially in reducing the dose of steroids.
  • A spray product containing topical corticosteroid (hydrocortisone aceponate) that is not absorbed into the body has been shown to be useful both to control and, used less frequently but still regularly, to prevent flares.
  • Topical therapy is valuable in reducing the allergenic load on the skin Therapeutics: skin. This may be impractical for many cats but regular use of hypoallergenic or colloidal oatmeal containing shampoos Shampoo therapy is recommended for those few cats that tolerate or enjoy this process.

Monitoring

  • The only side-effect of hyposensitization is the rare anaphylactic reactions Anaphylaxis. The first few injections should be administered in surgery. Rarely get increase in pruritus but this is an indication for dose adjustment. The cat should be observed after every injection for 30 mins by someone who knows what to do in case of an allergic response.
  • Side-effects of glucocorticoid medication require monitoring, especially routine urinanalysis to detect occult urinary tract infections at least every six months.
  • Avoidance of flare factors, eg fleas, bacteria.

Subsequent Management

Treatment

  • Try to stabilize patient on lowest possible dose of alternate day prednisolone Prednisolone or methyl prednisolone Methylprednisolone.
    Increase in itch should prompt search for flare factors such as flea allergy dermatitis.
  • Hyposensitization regimes may take up to nine months to take effect.

Monitoring

  • Pruritus decreased.
  • Normalization of skin and haircoat.

Outcomes

Prognosis

  • Good if seasonally affected.
  • May develop multiple allergies over succeeding years   →   increased difficulty in control.

Expected Response to Treatment

Reasons for Treatment Failure

  • Failure to diagnose concurrent disease, eg flea allergy, food sensitivity or pyoderma.
  • Many cases become less responsive to glucocorticoids with the passage of time - frequently due to a failure to manage concurrent disease.
  • Inability of client to cope with treatment schedules.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Ravens P A, Xu B J & Vogelnest L J (2014) Feline atopic dermatitis: a retrospective study of 45 cases (2001-2012). Vet Dermatol 25 (2), 95-102 PubMed.
  • Schmidt V, Buckley L M, McEwan N A et al (2012) Efficacy of a 0.0584% hydrocortisone aceponate spray in presumed feline allergic dermatitis: an open label pilot study. Vet Dermatol 23 (1), 11-6 PubMed.
  • Wildermuth B E, Griffin C E & Rosenkrantz W S (2012) Response of feline esoinophilic plaques and lip ulcers to amoxicillin trihydrate-clavulanate potassium therapy: a randomized, double-blind placebo-controlled prosoective study. Vet Dermatol 23 (2), 110-8 PubMed.
  • Yu H W & Vogelnest L J (2012) Feline superficial pyoderma: a retrospective study of 52 cases (2001-2011). Vet Dermatol 23 (5), 448-e86 PubMed.
  • Favrot C, Steffan J, Seewald W et al (2011) Establishment of diagnostic criteria for feline nonflea-induced hypersensitivity dermatitis. Vet Dermatol 23 (1), 45-50 PubMed.
  • Wisselink M A & Willemse T (2009) The efficacy of cyclosporine A in cats with presumed atopic dermatitis: A double blind, randomised prednisolone-controlled study. Vet J 180 (1), 55-59 PubMed.
  • Last R D, Suzuki, Y, Manning T et al (2004) A case of fatal systemic toxoplasmosis in a cat being treated with cyclosporin A for feline atopy. Vet Dermatol 15 (3), 194-198 PubMed.
  • Moriello K A (2001) Feline atopy in three littermates. Vet Dermatol 12 (3), 177-181 PubMed.
  • Gilbert S & Halliwell R E (1998) Feline immunoglobin E - induction of antigen-specific antibody in normal cats and  levels in spontaneously allergic cats. Vet Immunol Immunopathol 63 (3), 235-252 PubMed.
  • Roosje P J, Whitaker-Menezes D, Goldschmidt M H et al (1997) Feline atopic dermatitis - a model for Langerhans cell participation in disease pathogenesis. Am J Pathol 151 (4), 927-932 PubMed.
  • Scott D W & Miller W H Jr. (1993) Medical management of allergic pruritus in the cat, with emphasis on feline atopy. J S Afr Vet Assoc 64 (2), 103-108 PubMed.

Other sources of information

  • Miller W H, Griffin C E & Campbell K L (2013) Feline Atopic Dermatitis. In: Muller & Kirk's Small Animal Dermatology 7th edn. Elsevier, Mosby, Missouri. pp 388-392.
  • Trimmer A M & Newton H M (2010) Rush and Conventional Immunotherapy. In:Consultations in Feline Internal Medicine volume 6. St Louis: Saunders, Elsevier, pp 358-367.
  • Foster A P & Roosje P J (2006) Update on Feline immunoglobulin E (IgE) and diagnostic recommendations for atopy. In: Consultations in Feline Internal Medicine volume 5. Edited by J R August. Elsevier Saunders, Missouri, pp 229-238.
  • Fadok V A (1995) Three feline dermatologic syndromes and their relationship to allergy. Proceedings of 1995 North American Conference Orlando, Florida Jan 14-18.

Other Sources of Information