Cutaneous immune-mediated diseases in cats can present with clinical signs of erythema, hair loss, scaling/crusting and erosions with or without pruritis, mimicking many differential diagnoses such as hypersensitivity dermatitis and infections (eg, parasitic and fungal dermatitis). Veterinarians are encouraged to become familiar with the characteristic clinical features of various immune-driven skin disorders to permit early diagnosis and appropriate treatment. Diagnosis and therapeutic management of feline immune-mediated skin diseases can be challenging. Although immune-mediated skin diseases in cats are rare, these can be associated with severe systemic clinical signs, which can lead to poor quality of life and owners electing euthanasia. In the first of a two-part article series, the clinical presentations of feline immune-mediated skin diseases related to the pemphigus complex, cutaneous lupus erythematosus, and thymoma- and non-thymoma-associated exfoliative dermatitis are reviewed and differential diagnoses, diagnosis and therapeutic approach are discussed. In Part 2, the equivalent is discussed for erythema multiforme, f Stevens-Johnson syndrome/toxic epidermal necrolysis spectrum, plasma cell pododermatitis, proliferative and necrotizing otitis externa, pseudopelade, alopecia areata and auricular chondritis. The information in this article is based on a review of the existing veterinary literature.

Practical relevanceCutaneous immune-mediated diseases in cats can present with clinical signs of erythema, hair loss, scaling/crusting, and erosions with or without pruritus, mimicking many differential diagnoses such as hypersensitivity dermatitis and infections (eg, parasitic and fungal dermatitis). Veterinarians are encouraged to become familiar with the characteristic clinical features of various immune-driven skin disorders to permit early diagnosis and appropriate treatment.Clinical challengesDiagnosis and therapeutic management of feline immune-mediated skin diseases can be challenging. Although immune-mediated skin diseases in cats are rare, these can be associated with severe systemic clinical signs, which can lead to poor quality of life and owners electing euthanasia.AimsIn the second of a two-part article series, the clinical presentations of the feline immune-mediated skin diseases erythema multiforme, Stevens-Johnson syndrome/toxic epidermal necrolysis spectrum, plasma cell pododermatitis, proliferative and necrotizing otitis externa, pseudopelade, alopecia areata and auricular chondritis are reviewed and differential diagnoses, diagnosis and therapeutic approach are discussed. In Part 1, the equivalent is discussed for feline immune-mediated skin diseases related to the pemphigus complex, cutaneous lupus erythematosus, and thymoma- and non-thyoma-associated exfoliative dermatitis.Evidence baseThe information in this article is based on a review of the existing veterinary literature.

Drug-induced skin disease or cutaneous adverse drug reactions (CADRs) are terms that encompass the clinical manifestations of the skin, mucosae and adnexa induced by a drug or its metabolites. The skin is the organ most frequently affected by drug reactions, which may affect up to 10% of hospitalized patients and occur in 1-3% of multimedicated patients. Most CADRs are mild or self-resolving conditions; however, 2-6.7% of could develop into potentially life-threatening conditions. CADRs represent a heterogeneous field and can be diagnostically challenging as they may potentially mimic any dermatosis. Currently, there are between 29-35 different cutaneous drug-reaction patterns reported ranging from mild dermatitis to an extensively burnt patient. The most frequently reported are maculopapular rash, urticaria/angioedema, fixed drug eruption and erythema multiforme. Less common but more severe patterns include erythroderma, drug reaction with eosinophilia and systemic symptoms, and Stevens-Johnson syndrome/toxic epidermal necrolysis spectrum. Almost any drug can induce a CADR, but antibiotics, nonsteroidal anti-inflammatory drugs and antiepileptics are the most frequently involved. Different mechanisms are involved in the pathogenesis of CADRs, although in some cases, these remain still unknown. CADRs could be classified in different ways: (i) type A (augmented) or type B (bizarre); (ii) immediate or delayed; (iii) immune-mediated or nonimmune-mediated; (iv) nonsevere or life-threatening; and (v) by their phenotype, including exanthematous, urticarial, pustular and blistering morphology. Recognizing a specific CADR will mostly depend on the ability of the physician to perform a detailed clinical examination, the proper description of the morphology of the skin lesions and supporting laboratory and/or skin biopsy findings.