Proliferative and necrotizing otitis externa in four cats

Cytotoxic dermatitis: Review of the interface dermatitis pattern in veterinary skin diseases

Interface dermatitis or lichenoid interface dermatitis refers to a cutaneous inflammatory pattern in which keratinocyte cell death is the essential feature. These terms have evolved from the originally described lichenoid tissue reaction. These lesions are the basis for an important group of skin diseases in animals and people where cytotoxic T-cell-mediated epidermal damage is a major pathomechanism. Yet, for largely historical reasons these commonly used morphological diagnostic terms do not reflect the essential nature of the lesion. An emphasis on subsidiary lesions, such as the presence of a lichenoid band, and definitions based on anatomical features, such as location at the dermo-epidermal location, may cause confusion and even misdiagnosis. This review covers historical aspects of the terminology, including the origin of terms such as "lichenoid." The types of cell death involved and the histopathologic lesions are described. Etiopathogenesis is discussed in terms of aberrations of immune/inflammatory mechanisms focusing on cutaneous lupus erythematosus, erythema multiforme, and Stevens-Johnson syndrome/toxic epidermal necrolysis. Mechanisms have most extensively been studied in humans and laboratory animals and the discussion is centered on these species. As interface dermatitis is firmly entrenched in dermatological parlance, rather than using "cytotoxic" as its substitute, the terminologies "interface cytotoxic dermatitis" and "panepidermal cytotoxic dermatitis" are recommended, based on location and extent of epithelium affected.

Extra-auricular lesions of proliferative and necrotizing otitis externa in three kittens

BACKGROUND

Proliferative and necrotising otitis externa (PNOE) is a rare disorder in cats with poorly understood pathogenesis. Extra-auricular (EA) lesions recently have been mentioned in a textbook and in one case report.

OBJECTIVES

To describe EA lesions associated with PNOE in three kittens.

ANIMALS

A 6-month-old female domestic short hair (DSH) cat (Case 1), an 8-month-old female DSH cat (Case 2) and a 5-month-old female DSH cat (Case 3).

METHODS AND RESULTS

All cases exhibited classical lesions of PNOE associated with EA lesions, generalised (cases 1 and 3) or limited to eyelids (Case 2). Lesions were characterised by thick, adherent, hyperkeratotic papules coalescing to plaques and attempts to remove the hyperkeratotic plaques resulted in erosions. Histopathological examinations revealed classical features of PNOE: severe acanthosis associated with a marked lymphocytic exocytosis, satellitosis and apoptotic keratinocytes at all levels of the epidermis and the outer root sheath of hair follicles. Cases 2 and 3 resolved spontaneously. Case 1 remained stable with topical tacrolimus and oral prednisolone after a short course of ciclosporin.

CONCLUSIONS AND CLINICAL IMPORTANCE

This report describes EA lesions of PNOE in three kittens. Such lesions may be underdiagnosed, and this report emphasises the role of a thorough clinical inspection in PNOE cases.

Chronic Otitis in Cats: Clinical management of primary, predisposing and perpetuating factors

PRACTICAL RELEVANCE

Chronic otitis can be one of the most frustrating diseases to manage for a small animal practitioner. While it occurs less commonly in the cat than the dog, it is no less challenging. The purpose of this review is to discuss the common and uncommon causes of chronic otitis in the cat within the clinical framework used for diagnosis and treatment. The focus is on diseases that affect the ear canal, rather than those restricted to the pinnae.

CLINICAL CHALLENGES

Otitis is multifactorial, which complicates management. A common clinical mistake is to focus solely on treating the infection present. Only by addressing all factors will a clinician successfully control chronic otitis. For the purposes of this review, the authors have adopted the established model of separating primary, predisposing and perpetuating causes of otitis. Primary factors are those that directly cause otitis (inflammation); predisposing factors are those that put the patient at risk for development of otitis; and perpetuating factors are those that result in ongoing clinical signs of otitis or that prevent clinical resolution.

AUDIENCE

This review is aimed at veterinarians who treat cats and particularly those with an interest in feline dermatology and otology.

EQUIPMENT

While many practitioners rely on a hand-held otoscope, a video-otoscope can be very helpful for the diagnosis and treatment of chronic otitis.

EVIDENCE BASE

This review presents up-to-date information regarding the diagnosis and treatment of chronic otitis in cats, with emphasis on the most recent peer-reviewed literature.

Distinguishing Between Dermatologic Disorders of the Face, Nasal Planum, and Ears: Great Lookalikes in Feline Dermatology

Facial dermatitis in cats can be caused by a broad range of infectious, allergic, immune-mediated and neoplastic disorders with very different treatments and prognoses. Baseline dermatologic diagnostics (skin scrapings for mites, cytology for infection and to characterize inflammatory infiltrate, and dermatophyte culture) are required, as well as possible further diagnostics, including therapeutic trials for parasites and feeding a hypoallergenic diet, bacterial culture, and skin biopsies for histopathology in order to achieve a diagnosis. Clinical presentations of diseases affecting different parts of the feline face are presented and discussed.

Contribution of oral triamcinolone to treating proliferative and necrotising otitis externa in a 14-year-old Persian cat

Case summary

A 14-year-old female spayed cat was referred for recurrent otitis externa and unusual proliferative lesions in both ear canals. The affected pinnae and external ear canals were covered with large reddish-to-dark-brown verrucous and necrotic tissue. Friable material and exudates occluded both ear canals. Proliferative lesions developed in both ears 2–3 weeks before referral. The histopathological diagnosis from two biopsies obtained from the friable materials with endoscopic biopsy forceps was proliferative and necrotising otitis externa (PNOE). Treatment was initiated with once-daily application of a potent topical glucocorticoid (mometasone furoate) to both ears. Although the auricle and vertical ear canals responded well, no improvement was seen in the horizontal part of the ear canal after 9 weeks. Therefore, oral triamcinolone (0.9 mg/kg q24h) was added for 1 week, and was then tapered (q48h) for 3 weeks. Most lesions resolved, and after a further 2 weeks of prednisolone (2 mg/kg q48h) there was complete resolution. No recurrence was observed during a 2 year follow-up period.

Relevance and novel information

PNOE commonly occurs in kittens, but it can develop in older cats. To our knowledge, the PNOE in this case is the oldest age of onset reported. This condition is rare and was only described recently, and therapeutic options appear limited. According to previously published reports, steroid therapy is ineffective, and tacrolimus is the only treatment known to achieve resolution. However, oral and topical glucocorticoids were beneficial in this case.

Topical ear treatment - options, indications and limitations of current therapy

Topical otic products form an integral part of the overall management of otitis externa. With an ever increasing array of ear drops and cleaners to choose from, appropriate selection of therapy can be difficult. The investigation of all cases of otitis externa should consider primary and secondary causes and predisposing and perpetuating factors. This article considers topical therapy under these same broad headings and discusses, through literature review, the various properties of the components of the ear cleaning solutions and drops.

Proliferative and necrotizing otitis externa in a kitten: successful treatment with intralesional and topical corticosteroid therapy

Proliferative and necrotising otitis externa (PNOE) is a very rare disease affecting the ear canals and concave pinnae of kittens. This report describes a 5-month-old cat with PNOE. Histopathological examination confirmed the diagnosis. Treatment was initiated with local injection of methylprednisolone acetate into the lesions. The cat was subsequently treated with clobetasol propionate cream, a potent topical glucocorticoid ointment. The cat showed marked improvement. While topical treatment with tacrolimus, an immunosuppressive agent, is reported to be an effective therapy, to the best of our knowledge, this is the first report to treat PNOE with local corticosteroid therapy.

Erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis: a comparative review

BACKGROUND

Human erythema multiforme (EM) and Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) are separate conditions. There is no consensus on classification criteria for the eponymous diseases in animals.

RESULTS

Animal EM is very different from 90% of human EM, which is herpes virus associated (HAEM). Animals lack acrally distributed, typical raised targets. Unlike canine parvovirus 'EM', HAEM is not an active infection. Animal EM is often attributed to drugs, but this is rarely proved. Conversely, human and animal SJS/TEN are almost identical, life-threatening disorders of epidermal necrosis and detachment, typically triggered by drugs (occasionally by infectious agents). Both EM and SJS/TEN are mediated by cytotoxic lymphocyte responses against altered keratinocytes (infectious agents or drugs). Apoptosis results from direct cytotoxicity or through soluble mediators, namely Fas ligand, granzymes, perforin and granulysin. Diagnosis in humans is clinicopathological, with emphasis on clinical lesions; histopathology confirms the pathological process as interface (cytotoxic) dermatitis. Human EM is self-limiting; only recurrent and rare persistent cases require antiviral/immunosuppressive therapies. Drug-induced EM responds to drug withdrawal. Idiopathic canine EM (>40%) is usually chronic, refractory to treatment and may represent heterogeneous conditions. Early identification and removal of the causative drug and high-quality supportive care are critical in SJS/TEN. Mortality rate is nevertheless high.

CONCLUSIONS AND CLINICAL IMPORTANCE

(1) Histopathological lesions do not reliably differentiate EM, SJS and TEN. (2) A multicentre study to develop a consensus set of clinical criteria for EM and SJS/TEN in animals is overdue. (3) No adjunctive therapies, including intravenous immunoglobulin and ciclosporin, have met evidence-based standards.

Cat favus caused by Microsporum incurvatum comb. nov.: the clinical and histopathological features and molecular phylogeny

Favus is a distinctive form of infection that is caused by exclusively dermatophytes. Its clinical presentation is characterized by scutula, which are concave, thick fungal crusts. The best-known examples of human scalp favus are caused by Trichophyton schoenleinii and those of mouse favus are caused by T. quinckeanum. However, other dermatophytes, such as T. violaceum, T. verrucosum, Microsporum audouinii, M. gallinae, M. gypseum, and M. canis, have been reported sporadically to cause favic lesions. Favus on cats has rarely been mentioned in the literature, and the pathogens with which it has been associated are, for the most part, unknown. Here, we examine four cat favus cases, focusing on clinical presentations and histopathological features. In all cases the etiologic agent was identified as M. incurvatum based on its morphological characteristics and sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA. Phylogenetic analysis using the neighbor-joining method, which is based on ITS, showed that these four isolates belonged to two strains of M. incurvatum; one strain was a new combination from the basionym Nannizzia incurvata.

Proliferative and necrotising otitis externa in a cat without pinnal involvement: video-otoscopic features

Proliferative and necrotising otitis externa is a rare and recently described disease affecting the ear canals and concave pinnae of kittens. This article describes a case of proliferative and necrotising otits externa in a young adult cat. In this case, the lesions did not affected the pinnae, but both ear canals were severely involved. Video-otoscopy revealed a digitally proliferative lesion, growing at 360° all around the ear canals for their entire length, without involvement of the middle ear. Histopathological examination confirmed the diagnosis, and the cat responded completely to a once-daily application of 0.1% tacrolimus ointment diluted in mineral oil in the ear canals. Video-otoscopy findings, not described previously, were very peculiar and may help clinicians to diagnose this rare disease.

PNPLA1 mutations cause autosomal recessive congenital ichthyosis in golden retriever dogs and humans

Ichthyoses comprise a heterogeneous group of genodermatoses characterized by abnormal desquamation over the whole body, for which the genetic causes of several human forms remain unknown. We used a spontaneous dog model in the golden retriever breed, which is affected by a lamellar ichthyosis resembling human autosomal recessive congenital ichthyoses (ARCI), to carry out a genome-wide association study. We identified a homozygous insertion-deletion (indel) mutation in PNPLA1 that leads to a premature stop codon in all affected golden retriever dogs. We subsequently found one missense and one nonsense mutation in the catalytic domain of human PNPLA1 in six individuals with ARCI from two families. Further experiments highlighted the importance of PNPLA1 in the formation of the epidermal lipid barrier. This study identifies a new gene involved in human ichthyoses and provides insights into the localization and function of this yet uncharacterized member of the PNPLA protein family.

Cornification defect in the golden retriever: clinical, histopathological, ultrastructural and genetic characterisation

Veterinarians have recognised a nonpruritic skin disease in the Golden retriever breed characterised by excessive scaling of large, variably pigmented flakes of skin in otherwise healthy dogs. This prospective case series describes clinical, histopathological, ultrastructural and genetic features of this cornification defect in 17 affected dogs. The condition affects young dogs of either sex and is characterised by symmetrical, predominantly ventro-lateral scaling and hyperpigmentation of the trunk. Histopathological and ultrastructural changes of the stratum corneum are suggestive of delayed degradation of corneodesmosomes. A genetic aetiology is proposed and a single-trait autosomal recessive mode of inheritance discussed.