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Background: Cytological detection of acantholytic keratinocytes (acantholytic cells [AC]) helps to identify canine pemphigus foliaceus (cPF) yet AC also occurs in superficial pyoderma (SP), the main differential diagnosis., Hypothesis/objectives: To compare selected cytomorphological features of cPF and SP and to establish cytological diagnostic criteria that could differentiate cPF from SP., Animals: 40 and 51 client-owned dogs with PF and SP, respectively., Materials and Methods: Impression smears from cPF (64), impetigo (40) and exfoliative superficial pyoderma (ESP) (17) samples were stained with Romanowsky stain, randomised, blinded and evaluated by two investigators independently. The entire sample was screened (×500 or ×1000 magnification) for round (AC1), boat (AC2) and raft AC, eosinophils and bacteria. Interobserver agreements were calculated., Results: The average number of the 10 highest ×500 fields for AC1 and AC2 was significantly higher in PF than SP (p < 0.0001; Kruskal-Wallis test). Rafts and eosinophils were more common in PF than SP (p < 0.0001; chi-square test), while bacteria were rare in PF (5%; p < 0.0001; chi-square test). Observations between the experienced and novice investigators were highly correlated. An ROC analysis identified five AC1/×500-magnification field as a suitable cut-off value for predicting PF diagnosis. This cut-off value was tested by two additional investigators, who identified sensitivity of 84%-100%, specificity of 95%-97% and accuracy of 95%-96% for the diagnosis of cPF., Conclusions and Clinical Relevance: Criterion-based impression smear cytological evaluation can provide strong evidence to support the clinical diagnosis. Acantholytic cell morphology varies in cPF and SP, and experience can improve accuracy in cytological differentiation., (© 2024 The Author(s). Veterinary Dermatology published by John Wiley & Sons Ltd on behalf of ESVD and ACVD.)

Background: While the clinical features were described recently, the histopathological characterisation of trunk-dominant canine pemphigus foliaceus (PF) is lacking, and whether it differs from classic facial or insecticide-triggered PF is unknown., Hypothesis/objectives: This study describes the histopathological findings of trunk-dominant PF, and compares the results to classic facial and insecticide-triggered PF., Animals: Skin biopsies from 103 dogs with clinically characterised trunk-dominant (n = 33), classic facial (n = 26) and insecticide-triggered PF (n = 44) were included., Materials and Methods: Histological sections, randomised and blinded, were scored for over 50 morphological parameters of pustules, epidermis, dermis, adnexa and crusts. Intact pustule area and width were measured by digital microscopy., Results: In trunk-dominant PF, 77 intact pustules were predominantly subcorneal (0.0019-1.940 mm 2 area, 0.0470-4.2532 mm wide), and contained from one to over 100 acantholytic keratinocytes. Pustules had boat acantholytic cells, corneocytes, perinuclear eosinophilic rings, neutrophil rosettes, acantholytic cell necrosis, rafts, cling-ons and/or eosinophils. Peripustular epidermal spongiosis, necrosis and lymphocyte exocytosis occurred, as did follicular pustules. Mixed dermal inflammation often contained eosinophils. Trunk-dominant PF did not differ from the other PF groups except for few parameters, such as having fewer rafts (p = 0.003). Additional autoimmune inflammatory patterns occurred in all PF groups., Conclusions and Clinical Relevance: Trunk-dominant PF and other canine PF variants are histologically similar, which indicates shared pathomechanisms. The identification of common boat acantholytic cells and corneocyte separation has implications for the mechanisms of acantholysis. The diversity of histopathological and polyautoimmunity features support complicated immune mechanisms. Finally, results indicate that diagnostic biopsies cannot differentiate between these PF variants in dogs., (© 2023 The Authors. Veterinary Dermatology published by John Wiley & Sons Ltd on behalf of ESVD and ACVD.)

Background: A new canine subgroup defined as 'old-dog' or 'hyperkeratotic' erythema multiforme (HKEM) with marked hyperkeratosis and parakeratosis has been proposed without any detailed description of larger case series., Objectives: We report herein the signalment, clinical signs, treatment outcome, and histopathological and immunological findings in 17 dogs with HKEM., Animals: Inclusion criteria were the presence of (i) scaly skin lesions with or without crusting; and (ii) microscopic lesions typical of EM (i.e. a panepidermal cytotoxic lymphocytic dermatitis with or without basal keratinocyte apoptosis); and (iii) microscopic ortho- and/or parakeratotic hyperkeratosis affecting the interfollicular epidermis., Materials and Methods: Clinical questionnaires and skin biopsies were reviewed. Polymerase chain reactions for epidermotropic viruses and direct immunofluorescence were performed., Results: Various breeds were affected with an over-representation of males in their mid-to-late adulthood (median age 9 years). Generalised skin lesions included multifocal-to-coalescing, linear and annular macules and plaques with erythema and adherent firm crusting. Microscopic lesions were specific for EM and featured prominent superficial epidermal apoptosis with lymphocytic satellitosis and parakeratosis. No drug triggers were identified. Polymerase chain reactions for canine herpesvirus polymerase gene, canine parvovirus and canine distemper virus were negative in all HKEM and canine erosive EM (15 dogs) biopsies. Lesions failed to respond to oral and/or topical antimicrobials. Complete remission of signs was achieved in 9 of 17 dogs (53%) using immunosuppressive regimens., Conclusions and Clinical Relevance: Hyperkeratotic erythema multiforme (HKEM) is a chronic, persistent and clinically distinctive erythema multiforme (EM) variant that differs from 'classic' vesiculobullous erosive-to-ulcerative EM in dogs., (© 2022 ESVD and ACVD.)

Background: Canine trunk-dominant pemphigus foliaceus (PF) is mentioned rarely in the literature., Hypothesis/objectives: The goal of this study was to provide clinical description of trunk-dominant PF and to demonstrate the prevalence of serum antikeratinocyte, anti-desmocollin-1 (DSC1) and anti-desmoglein-1 (DSG1) antibodies, and determine their diagnostic value in this particular PF phenotype., Materials and Methods: Clinically relevant information was collected from 31, 25 and 34 dogs with trunk-dominant and facial PF and superficial pyoderma (SP), respectively. Sera from these dogs were tested for antikeratinocyte, anti-DSC1 and anti-DSG1 antibodies using indirect immunofluorescence on canine tissues and DSC1- and DSG1-transfected cells. Sera from healthy dogs and dogs with clinically irrelevant diseases served as controls., Results: Footpad involvement and grouped/polycyclic lesion organisation were identified as features of both PF phenotypes, and not of SP. Antikeratinocyte immunoglobulin (Ig)G was not specific for canine PF. By contrast, antigen-specific IgG was detected only in PF sera; anti-DSC1 IgG in 100% and 58% of dogs with facial and trunk-dominant PF, respectively, and anti-DSG1 IgG in 7% of dogs with trunk-dominant PF only., Conclusions: Trunk-dominant PF shares DSC1 as a major autoantigen with facial PF. The ability to detect anti-DSC1 IgG is lower in trunk-dominant PF, yet despite the lower sensitivity, the positive predictive value and accuracy of this particular anti-DSC1 IgG test are high. A negative test result, however, cannot exclude the diagnosis, and characteristic clinical features such as footpad involvement and/or grouped/polycyclic lesions must be considered when distinguishing trunk-dominant PF from its most relevant differential diagnosis: SP., (© 2022 ESVD and ACVD.)

Background: Junctional epidermolysis bullosa (JEB) is a group of congenital blistering skin diseases characterized by clefting through the lamina lucida of the basement membrane zone., Objectives: To characterize the clinical and morphological features of a congenital mechanobullous disease in a litter of puppies with severe upper respiratory involvement, and to identify an associated genetic variant., Animals: Five of eight puppies in an Australian cattle dog cross-bred litter showed signs of skin fragility. Three were stillborn and one died at one month of age. The two surviving puppies were presented with blistering skin disease and severe respiratory distress. Additionally, one unaffected sibling was examined and blood was obtained for genetic testing., Methods and Materials: Post-mortem examination, histopathological evaluation and electron microscopy were performed. Whole genome sequencing (WGS) of one affected puppy was compared to a database of 522 dogs of 55 different breeds for variant analysis. Sanger sequencing of one additional affected and one unaffected sibling confirmed the variant., Results: Clinically, severe mucocutaneous ulcers occurred in frictional areas with claw sloughing. Histopathological results revealed subepidermal clefts and electron microscopy confirmed the split in the lamina lucida. Post-mortem examination documented extensive pharyngeal and laryngeal lesions with granulation tissue and fibrinous exudate obscuring the airway. Moderate tracheal hypoplasia contributed. The WGS revealed a novel missense variant in the laminin α3-chain XP&#95;537297.2p(Asp2867Val), with an autosomal recessive mode of inheritance., Conclusions and Clinical Relevance: A novel variant in LAMA3 caused a generalized and severe phenotype of JEB with an unique clinical presentation of upper airway obstruction., (© 2021 the European Society of Veterinary Dermatology and the American College of Veterinary Dermatology.)

Background: Bullous amyloidosis is a rare disease in humans that has not been described in a veterinary species in the peer-reviewed literature. The human disease is characterised by haemorrhagic vesicles and bullae on the skin and mucosae, which form due to amyloid deposition., Hypothesis/objectives: To describe the clinical features, laboratory analysis and histopathological features of an unique presentation of bullous disease in a horse., Animals: A 17-year-old thoroughbred mare presented for weight loss and severe oral cavity ulcers., Methods and Materials: Investigations involved haematological evaluation, chemistry profiles, gastroscopy and serum protein electrophoresis, and, postmortem, histopathological evaluation, Congo-red staining and transmission electron microscopy (TEM)., Results: Haemorrhagic vesicles and bullae occurred on the mucosa of the oral cavity, lips, oesophagus and stomach, and much less the muzzle, face and mucocutaneous areas of the perineum, where scarring was evident. Histopathological evaluation and Congo-red staining confirmed the presence of amyloid deposits in dermis and submucosa, in association with vesicle and bulla formation, consistent with bullous amyloidosis. TEM confirmed amyloid fibril deposition in the dermis and along the basement membrane zone. Clefts occurred in the superficial dermis and submucosa, which explained haemorrhage and scarring. The presence of a polyclonal gammopathy and the rapid abolishment of Congo-red staining with performate pretreatment supported serum amyloid A and secondary amyloidosis., Conclusion and Clinical Importance: Bullous amyloidosis is a novel disease of the horse and a newly recognised differential for bullous disease, for which the haemorrhagic nature of bullae, scarring and deep secondary ulcers are considered clinical clues to the condition., (© 2021 the European Society of Veterinary Dermatology and the American College of Veterinary Dermatology.)

Background: Hyperkeratotic erythema multiforme (HKEM) is a clinically distinct dermatosis and poorly characterized syndrome, comprised of hyperkeratotic plaques with variable symmetry and apoptosis similar to "classic" erosive canine EM. Hyperkeratotic EM has a protracted clinical course and, although treatments with glucocorticoids, azathioprine and/or ciclosporin have been tried, rates of remission are low., Objectives: To describe successful treatment of HKEM in two dogs using oclacitinib., Animals: A 7-year-old, spayed Havanese dog (Case 1) and a 1-year-old, intact cryptorchid Dachshund dog (Case 2)., Methods: Case characterization and clinical diagnoses were based on lesion character, surgical biopsy, cytological evaluation, culture, direct immunofluorescence (DIF) and expected responses to treatments., Results: Both cases exhibited multifocal, often symmetrical hyperkeratotic plaques with adherent scale. Histological findings revealed prominent epidermal hyperplasia, parakeratotic hyperkeratosis, lymphocytic dermatitis and transepidermal apoptosis with lymphocytic satellitosis. DIF revealed fine, patchy IgG, IgM and IgA basement membrane deposits (Case 2). Both dogs exhibited rapid improvement with oral oclacitinib (0.6-0.9 mg/kg twice daily) with a complete remission of clinical signs observed in 12 and seven weeks in cases 1 and 2, respectively., Conclusion and Clinical Importance: Oclacitinib could be considered as a fast-acting and effective treatment option for HKEM in dogs., (© 2020 ESVD and ACVD.)

Background: Polyautoimmunity, the concurrent expression of two or more distinct autoimmune diseases (ADs) in a single individual, is a known phenomenon in humans and has been rarely reported in dogs. To the best of the authors' knowledge, comorbid pemphigus foliaceus (PF) and generalized discoid lupus erythematosus (GDLE) has not been reported in dogs., Hypothesis/objectives: To describe the clinical, histological and immunological features and treatment outcome of two unrelated dogs with comorbid PF and GDLE., Animals: One 10-year-old, spayed German shepherd dog and one 8-year-old, castrated American Staffordshire terrier presented for evaluation of a symmetrical, facial- and/or pedal-dominant pustular dermatitis with concurrent, truncal scaly plaques., Methods: For each dog, clinicopathological characterization included physical examination, lesion cytological evaluation, bacterial culture and sensitivity testing, skin histopathological investigation and direct and indirect immunofluorescence testing. Additional diagnostic imaging and haematological testing was performed to exclude extracutaneous disease., Results: Both dogs exhibited lesions clinically and histologically compatible with PF and GDLE. Moreover, one dog exhibited generalized leucotrichia and chronic superficial keratitis. Remission was achieved with immunosuppressive dosages of prednisolone [high-dose pulse (Case 1) or standard immunosuppressive dosage (Case 2)] and ciclosporin (5-6 mg/kg/day). Tissue-bound antikeratinocyte immunoglobulin (Ig)G and IgM were detected in both dogs. A weak basement membrane zone deposit of C3 was seen in one dog. Circulating antikeratinocyte and anti-desmocollin-1 IgG were detected in one dog., Conclusions and Clinical Importance: Cutaneous polyautoimmunity can occur in the dog. Depending on the specific disease combinations, overlapping clinical features may present diagnostic and/or therapeutic challenges. Moreover, these cases should be monitored for development of additional cutaneous or extra-cutaneous AD(s)., (© 2020 ESVD and ACVD.)

Background: Ischaemic dermatopathy represents a heterogenous and poorly-characterized canine syndrome that is often refractory to conventional immunosuppression. Janus-kinase inhibitors (JAKinibs) are used for the treatment of various human autoimmune diseases, including dermatomyositis. Oclacitinib is a generally well-tolerated, veterinary-approved, nonselective JAKinib that has therapeutic potential as an immunosuppressant., Hypothesis/objectives: To describe four cases of treatment refractory juvenile-onset ischaemic dermatopathy that rapidly and durably responded to oclacitinib administration., Animals: Four mixed-breed dogs, three 9-month-old male littermates and one 6-month-old female, were presented for generalized patchy alopecia, scarring and ulcerative dermatitis. Microscopic skin lesions were consistent with a severe ischaemic dermatopathy., Methods and Materials: A complete remission of skin lesions could not be achieved in any dog with glucocorticoids alone, nor when these were combined with adjuvant immunosuppressants. Oclacitinib treatment was then initiated at the dosage of 0.4-0.7 mg/kg twice daily, along with a tapering regimen of oral prednisolone., Results: A full clinical remission was achieved within four weeks of starting this combination therapy, with prednisolone being stopped within eight weeks thereof. Remission was maintained in two dogs with lower doses or dosing frequencies of oclacitinib, whereas the two others required persistent twice daily administration of this JAKinib., Conclusions and Clinical Importance: Oclacitinib was a useful immunosuppressive adjuvant to oral glucocorticoids for the treatment of refractory or severe cases of ischaemic dermatopathy in these four dogs. Such observation warrants further studies of the safety, efficacy and mechanism of action of oclacitinib as an immunosuppressant., (© 2019 ESVD and ACVD.)

Background: The microscopic and microbial features of the spreading epidermal collarettes of canine exfoliative superficial pyodermas are poorly characterized., Objectives: To characterize the clinical, cytological, microbial and histopathological features of epidermal collarettes in five dogs., Results: Cytology from the margins of collarettes identified neutrophils, extracellular and intracellular cocci within neutrophils but no acantholytic keratinocytes. Phenotypic and genotypic analyses identified all bacterial isolates from the centre and margin of five epidermal collarettes as Staphylococcus pseudintermedius. PCRs of collarette-associated Staphylococcus strains did not amplify genes encoding for the known exfoliative toxins expA and expB, whereas the predicted siet and speta amplification products were detected in all isolates. Microscopically, epidermal collarettes consisted of interfollicular, epidermal spongiotic pustules. Advancing edges of lesions consisted of peripheral intracorneal clefts in the deep stratum disjunctum above an intact stratum compactum; they contained lytic neutrophil debris, bacterial cocci and fluid, but no acantholytic keratinocytes. This intracorneal location of bacteria was confirmed using Gram stains and fluorescent in situ hybridization with eubacterial- and Staphylococcus-specific probes. The indirect immunofluorescence staining patterns of desmoglein-1, desmocollin-1, claudin-1, E-cadherin and corneodesmosin were discontinuous and patchy in areas of spongiotic pustules, whereas only that of corneodesmosin was weaker and patchy in advancing collarette edges., Conclusion: Epidermal collarettes represent unique clinical and histological lesions of exfoliative superficial pyodermas that are distinct from those of impetigo and superficial bacterial folliculitis. The characterization of possible causative staphylococcal exfoliatin proteases and the role of corneodesmosin in collarette pathogenesis deserve further investigation., (© 2016 ESVD and ACVD.)

Background: Generalized discoid lupus erythematosus (GDLE) is a newly recognized canine variant of chronic cutaneous lupus erythematosus (CLE) that is not well characterized., Hypothesis/objectives: We report herein the signalment, clinical signs, treatment outcome, histopathology and immunological findings of 10 dogs with GDLE., Methods: Inclusion criteria were: (i) a >3 month history of generalized skin lesions indicating a chronic or recurrent nature; (ii) skin lesions resembling those of human GDLE; (iii) histopathology of CLE (lymphocyte-rich interface dermatitis). Direct immunofluorescence (IF) and antinuclear antibody serology were investigated whenever possible., Results: Various breeds were affected in their mid- to late adulthood. Selection criteria of generalized multifocal, annular ("discoid") to polycyclic plaques with pigment changes, erythematous margin, adherent scaling, follicular plugging and central alopecia were shown in all dogs. In nine dogs, plaques contained mild to moderate central scarring with depigmentation and/or hyperpigmentation. There were no dogs in which the disease progressed to systemic lupus erythematosus within a median follow-up of 2.5 years. Per inclusion criteria, interface dermatitis occurred with basement membrane zone (BMZ) thickening, suprabasal apoptosis and/or dermal fibrosis in some dogs. Infundibular interface folliculitis was common; it sometimes transitioned to mural folliculitis in lower follicle segments, and occurred with follicular and sebaceous gland atrophy. The direct IF revealed patchy deposition of immunoglobulin IgG and IgM at the BMZ. Lesions responded to a variety of treatments, including ciclosporin, hydroxychloroquine, topical tacrolimus and tetracycline/niacinamide. Relapses were common after medications were tapered., Conclusions and Clinical Importance: These observations support the existence of a canine homologue of human GDLE., (© 2016 ESVD and ACVD.)

Background: Mucous membrane pemphigoid (MMP) is a chronic autoimmune subepidermal blistering disease of dogs, cats and humans., Objectives: The goal of this study was to describe the clinical, histological and immunological features and treatment outcomes of canine MMP., Animals: Sixteen dogs were diagnosed with MMP based on the presence of mucosal- or mucocutaneous-predominant vesiculation and/or ulceration, histological confirmation of subepidermal clefting and an age of disease onset greater than 6 months., Results: Six of 16 dogs (38%) were German shepherd dogs and their crosses. The median age of disease onset was 6 years (range: 1-10 years). At the time of presentation, the dogs exhibited erosions and ulcers in the oral cavity (11 of 16; 69%), nasal (nine of 16; 56%), periocular (eight of 16; 50%) and genital (six of 16; 38%) regions. Haired skin lesions were less frequent (six of 16; 38%) and involved mostly concave pinnae. Information on treatment outcome was available for 11 dogs (69%). A complete remission (CR) of lesions was achieved in 10 of 11 dogs (91%). The median time to CR was 33 weeks (range: 6-64 weeks). Treatment regimens varied widely but six of 10 (60%) dogs received a combination of tetracycline antibiotic and niacinamide alone, or with another drug, at the time of CR. Forty percent of the dogs in which CR had occurred experienced lesion relapse upon drug dose reduction., Conclusions and Clinical Importance: Canine MMP is a chronic and relapsing disease requiring long term treatment. Combination therapy is often needed to achieve CR., (© 2016 ESVD and ACVD.)

Background: Caryospora bigenetica is an intracellular protozoan parasite in snakes and raptors (primary hosts) and rodents (secondary host). Experimental infection has been documented in mice, pigs and goats; natural infection in dogs is rare., Objectives: To describe the clinical presentation, histological features, treatment and outcome of a case of protozoal nodular dermatitis and panniculitis in a Rottweiler puppy caused by C. bigenetica., Results: The puppy presented with generalized subcutaneous nodules measuring up to 2 cm in diameter. Histopathology revealed marked suppurative to pyogranulomatous dermatitis and panniculitis with intralesional protozoal organism. PCR and DNA sequencing confirmed infection with C. bigenetica. Treatment with a combination of oral trimethoprim-sulfamethoxazole (TMS), pyrimethamine and high-dose clindamycin (20 mg/kg twice daily) resulted in resolution of lesions in 6 weeks. Discontinuation of the treatment 2 weeks later was followed by a rapid relapse of skin lesions. Clindamycin and TMS were restarted and all lesions resolved within 2 weeks; TMS was discontinued 4 weeks later due to adverse effects. The lesions remained in remission for 2 months while the puppy received clindamycin monotherapy before a second relapse of skin lesions occurred., Conclusion and Clinical Importance: To the best of the authors' knowledge, this is the first documentation of the treatment and outcome of C. bigenetica cutaneous infection in a dog. Although remission of clinical signs can be achieved with combination therapy of clindamycin and TMS, long-term management is challenging and relapses should be anticipated., (© 2015 ESVD and ACVD.)

Background: Epidermolysis bullosa acquisita (EBA) is a rare autoimmune subepidermal blistering disease of dogs and humans., Objectives: Our objectives were to describe clinical phenotypes, histopathology and treatment outcomes of canine EBA., Animals: Twenty dogs diagnosed with EBA based on a subepidermal blister formation and collagen VII autoreactivity., Results: Most dogs were young (median: 1.2-year-old) with a male-to-female ratio of 2.3:1. Nine of 20 dogs (45%) developed lesions before one year of age and 11 of 20 dogs (55%) were great danes. Tense vesicles and bullae (18 of 20; 90%) and deep erosions and ulcers (20 of 20; 100%) were the most common lesions and these affected predominantly the oral cavity (19 of 20; 95%), pinnae (16 of 20; 80%), axillae (15 of 20; 75%) and footpads (14 of 20; 70%). Histopathology identified neutrophilic perivascular dermatitis (17 of 17; 100%) without or with (12 of 17; 71%) eosinophils, which occasionally equalled (four cases) or outnumbered neutrophils (two cases). Subepidermal vesicles were either devoid of inflammation or contained neutrophils with or without eosinophils, fibrin and/or haemorrhage. A complete remission of skin lesions was obtained in 14 dogs with a median time of 58 days. Glucocorticoids were used in these dogs either as a monotherapy (3 of 14; 21%) or in combination with other immunomodulating drugs (11 of 14; 79%). The median dose of prednisone was 3 mg/kg/day. The remaining six dogs were euthanized., Conclusions and Clinical Importance: Canine EBA is a rare subepidermal blistering disease with an inflammatory phenotype and a predilection for young great danes and male dogs. The outcome of treatment appears more favourable than assumed previously., (© 2015 ESVD and ACVD.)

Objective: To describe the clinical, histopathologic and immunohistochemical characteristics of an equine ocular inflammatory disease resulting in anterior uveitis and corneal endothelial inflammation associated with iris pigment dispersion and retrocorneal fibrous membrane (RFM) formation., Design: Retrospective study., Animals Studied: Sixteen horses with evidence of pigmented keratic precipitates (KPs), corneal edema, and/or iris depigmentation. Information collected from the medical records included signalment, clinical signs, prereferral treatment duration and response to therapy, ophthalmic examination findings, postreferral treatment, response to therapy, and outcome., Results: Twenty-one eyes from 16 horses were affected. Age ranged between 9 and 25 years (Average 16.1 years). Blepharospasm, epiphora, and/or corneal opacification were the first clinical signs noted. At the time of referral pigmented KPs, corneal edema, iridal depigmentation, and retrocorneal membranes were commonly seen. Treatment included topical and/or systemic anti-inflammatories and antibiotics with variable response. Reduction or cessation of anti-inflammatory therapy resulted in worsening of clinical signs and disease progression. Eight eyes ultimately required enucleation. Histopathology changes include iridal pigment loss and dispersion, RFM formation, and keratitis. Variable degrees of lymphoplasmacytic inflammation were dominated by T-cells within the corneal stroma, RFM, iris, and ciliary body with occasional multinucleated giant cells., Conclusions: Heterochromic iridocyclitis with secondary keratitis (HIK) is characterized by uveal inflammation with pigment dispersion and suspected corneal endothelial dysfunction. Horses being treated for HIK require diligent and frequent follow-up examinations in combination with aggressive local immune suppression to control the disease. However, HIK may not respond to therapy and enucleation may ultimately be required to ensure the horse's comfort., (© 2014 American College of Veterinary Ophthalmologists.)

Background: The diagnosis of dogs with chronic juxtamucosal erosive lesions and histopathology typical of cutaneous lupus erythematosus (CLE) is unclear., Hypothesis/objectives: We report herein 21 dogs with mucocutaneous erosive lesions and lupus-specific histopathology that we propose to be affected with mucocutaneous lupus erythematosus (MCLE), another variant of chronic CLE., Methods: Inclusion criteria were the presence of the following: (i) a >2 month history of chronic or recurrent skin lesions; (ii) erosions or ulcers predominating at mucosae or mucocutaneous junctions; (iii) microscopic lesions of CLE (i.e. a lymphocyte-rich interface dermatitis with basal keratinocyte damage); and (iv) a lack of complete remission following antimicrobials. Clinical questionnaires and skin biopsies were reviewed. Direct immunofluorescence and antinuclear antibody serology were performed whenever possible., Results: More than half of the 21 dogs were German shepherds or their crosses. The disease affected mostly dogs in their mid-adulthood and there was an over-representation of females. Erosions and ulcers predominated at genital/perigenital and anal/perianal areas, with a lower frequency of involvement of periocular, perioral and perinasal regions. In these dogs, there were no clinical signs suggestive of an associated systemic lupus erythematosus. Microscopic lesions were specific for CLE, but they were patchy and often infected with bacteria. The most common immunological finding was focal IgG deposition at the basement membrane zone. Lesions responded to varying interventions, but oral glucocorticoids led to a shorter time to complete remission. Relapses were common upon treatment tapering., Conclusions and Clinical Importance: These observations support MCLE being another variant of canine CLE., (© 2015 ESVD and ACVD.)

Background: Pemphigus foliaceus (PF) can occur spontaneously or as a reaction pattern associated with cutaneous adverse drug reactions., Hypothesis/objectives: To provide clinical, histological and immunological assessments of three dogs that developed cutaneous adverse drug reactions following application of a topical flea and tick control product, which contained dinotefuran, pyriproxyfen and permethrin., Animals: Three client-owned dogs., Results: The dogs exhibited rapid onset of papules, pustules and crusts at the site of application of the flea control product. In two dogs, the lesions became generalized, while the third exhibited a localized phenotype. Both dogs with generalized lesions required immunosuppressive treatment; one achieved remission after 1 year of treatment and one was euthanized due to adverse effects of glucocorticoids. The dog with a localized phenotype was treated with topical glucocorticoids exclusively and achieved remission after 10 months. Histology revealed subcorneal pustular dermatitis, with acantholysis of keratinocytes and focal to multifocal full-thickness epidermal necrosis. These features are similar to those previously reported for pesticide-triggered and spontaneous PF. Tissue-bound IgG was detected in two of three dogs, and autoantibodies targeting canine desmocollin-1 were identified in the serum of the one dog from which a sample was available., Conclusions and Clinical Importance: Cutaneous adverse drug reaction caused by a flea control product containing dinotefuran, pyriproxyfen and permethrin closely resembled those reported for other pesticide-associated PF-like cutaneous adverse drug reactions. Although it appears to be a rare entity, clinicians and pathologists should be aware of the potential for flea and tick control products to trigger PF-like reactions., (© 2015 ESVD and ACVD.)

Background: Bartonella henselae, a Gram-negative, zoonotic Alphaproteobacteria that infects erythrocytes, endothelial cells and dendritic cells, has previously been implicated as a cause of panniculitis in dogs and a human., Animal and Owner: An 8-year-old, spayed female Labrador retriever and its 78-year-old male owner living in the same household., Methods and Results: When preliminary and advanced testing failed to identify the cause of near-simultaneous-onset dermatological lesions, Bartonella serology, Bartonella Alphaproteobacteria growth medium (BAPGM) enrichment blood culture/PCR and immunohistochemistry were used to test specimens from the dog and owner. Bartonella henselae, genotype San Antonio 2 DNA was amplified and sequenced from the man's BAPGM enrichment blood culture and the dog's panniculitis lesion. The bacterium was visualized by immunohistochemistry in the dog's panniculitis lesion; however, neither the dog nor the owner was B. henselae seroreactive. Antibiotic therapy elicited dermatological improvement in both dog and owner., Conclusions and Clinical Importance: Bartonella henselae is an emerging zoonotic pathogen that induces granulomatous inflammatory lesions in various tissues of animals, including humans. We conclude that this bacterium had a contributory or causative role in the development of the dermatological lesions in the dog and owner., (© 2014 ESVD and ACVD.)

Background: Generalized discoid lupus erythematosus (DLE) is an autoimmune skin disease variant rarely reported in dogs. The antimalarial immunomodulator hydroxychloroquine has been suggested as maintenance therapy for generalized DLE in one dog, but several recurrences were noted in the 1 year follow-up of that patient., Hypothesis/objective: To describe the effective treatment of generalized DLE with ciclosporin in one dog., Animal: A 6-year-old, castrated male crossbred dog was presented with pruritic, well-demarcated annular to polycyclic, hyperpigmented plaques with marginal erythema on the dorsal head, neck, trunk and medial extremities; these had been nonresponsive to treatment with doxycycline and niacinamide., Methods: Investigation included complete blood count, serum chemistry profile, urinalysis, serum antinuclear antibody test, histopathological examination and direct immunofluorescence testing of skin biopsies., Results: The presence of lymphocyte-rich interface dermatitis on histology, together with generalized chronic recurrent hyperpigmented plaques, was consistent with the diagnosis of a generalized variant of DLE. The absence of systemic signs and unremarkable laboratory tests excluded concurrent systemic lupus erythematosus. Treatment was initiated with oral dexamethasone and ciclosporin. After 1 month, dexamethasone was discontinued and oral ketoconazole was added to the therapeutic regimen. Four months later, pruritus and erythema resolved, with most skin lesions becoming impalpable. Over the last 6 months, the patient's DLE was maintained in remission with oral ciclosporin and ketoconazole in combination every 3 days., Conclusions and Clinical Importance: The combination of ciclosporin and ketoconazole appeared effective to induce and maintain lesion remission in this dog with generalized DLE., (© 2014 ESVD and ACVD.)

Background: A recently launched topical ectoparasiticide containing fipronil, amitraz and S-methoprene has been associated with the development of an acantholytic pustular dermatitis similar to that of Promeris-triggered pemphigus foliaceus (PF)., Hypothesis/objectives: Our objectives were to describe the clinical, histological and immunological features of this PF-like cutaneous adverse drug reaction., Animals: Twenty-one dogs with a probable or definitive diagnosis of PF-like cutaneous adverse drug reaction were identified between May 2012 and February 2013., Material and Methods: Histology, direct and indirect immunofluorescence were employed to address the study objectives., Results: Most dogs were middle-aged or older (median, 9 years) and of large size (median, 23 kg). In six dogs (29%), the PF-like lesions remained confined to the site of application, while 15 dogs (71%) exhibited lesions at distant sites. One or two applications of the ectoparasiticide were sufficient to trigger PF-like lesions in seven (33%) and six (29%) dogs, respectively. Systemic signs were reported in nine dogs (43%), all with lesions extending to sites distant from application areas. Tissue-bound antikeratinocyte IgG was detected in the lesional epidermis of eight of 19 (42%) cases by direct immunofluorescence, while serum antikeratinocyte IgG was detected in 10 of 14 (71%) cases by indirect immunofluorescence. Autoantibodies were found to target canine desmocollin-1 in 11 of 14 dogs (79%), but not canine desmoglein-1, by indirect immunofluorescence on transfected cells. These immunological findings were similar in cases with localized and distant disease., Conclusions and Clinical Importance: This new topical ectoparasiticide containing fipronil, amitraz and S-methoprene is capable of triggering the development of an acantholytic pustular dermatosis that is a clinical, histological and immunological close match for Promeris-triggered PF and naturally occurring autoimmune PF in dogs., (© 2014 ESVD and ACVD.)

Background: In humans, rapidly developing Pasteurella multocida cellulitis after a cat scratch or bite is a well-known entity that sometimes progresses to necrotizing fasciitis and can be fatal., Case Report: A 3-year-old female spayed whippet dog developed ecchymosis, swelling and pain within 24 h of being scratched by a cat on the ventral thorax. Over the following days, while being treated only with pain medications, the lesions rapidly progressed into haemorrhagic bullae with expanding skin necrosis. A heavy growth of P. multocida was seen on bacterial cultures, and histological examination showed marked, suppurative panniculitis with necrosis of the epidermis, dermis and panniculus. Special histological stains highlighted a moderate amount of Gram-negative coccobacilli admixed with inflammatory cells. Complete resolution was achieved with surgical debridement, skin grafting and intravenous antibiotic treatment. Positive bacterial culture for P. multocida, in conjunction with the history, clinical findings, histology results and the rapid response to therapy, strongly supports a diagnosis of P. multocida necrotizing cellulitis., Conclusions and Clinical Importance: Complications of cat bite-associated P. multocida infections in humans are well known. To the authors' knowledge, this is the first documentation of P. multocida necrotizing cellulitis in a dog following a cat scratch wound. This case highlights the rapidity and severity of P. multocida cellulitis, if not recognized and treated early. Veterinarians should include P. multocida in the differential diagnosis of any local wound infection following a cat scratch., (© 2013 The Authors. Veterinary Dermatology © 2013 ESVD and ACVD.)

Background: In humans, necrolytic migratory erythema (NME) is a syndrome with a characteristic skin rash that is associated most often with a pancreatic glucagonoma and is recognized as part of the glucagonoma syndrome. In veterinary medicine, NME (also called as superficial necrolytic dermatitis, hepatocutaneous syndrome or metabolic epidermal necrosis) has been described in dogs in association with chronic liver diseases or, less frequently, glucagonoma, but NME associated with glucagonoma has not previously been reported in cats., Case Report: A 6-year-old male neutered domestic short hair cat was diagnosed with NME associated with a glucagon-producing primary hepatic neuroendocrine carcinoma (hepatic carcinoid). The cat presented with a 2 week history of vomiting and anorexia, and a 5-cm-diameter liver mass was detected by abdominal ultrasound. The cat exhibited general weakness, crusted skin lesions and pain in all four limbs. It was euthanized 11 months after the initial presentation. Histopathological review of the paw pads revealed the classic 'red, white and blue' lesion composed of parakeratotic hyperkeratosis, epidermal hydropic change and hyperbasophilia of the deep epidermis. The liver mass was diagnosed as a neuroendocrine carcinoma (hepatic carcinoid). Neoplastic cells were strongly immunoreactive for glucagon., Conclusion and Clinical Importance: This is the first case report of NME associated with a glucagon-producing primary hepatic neuroendocrine carcinoma in a cat., (© 2013 The Authors. Veterinary Dermatology © 2013 ESVD and ACVD.)

Background: Patch tests with allergens are used for the evaluation of cellular hypersensitivity to food and environmental allergens in dogs and humans with atopic dermatitis. Viaskin is a novel allergen epicutaneous delivery system that enhances epidermal allergen capture by immune cells., Objectives: To compare the use of Viaskin and Finn chamber patch tests in dogs hypersensitive to mite allergens., Methods: Empty control or Dermatophagoides farinae house dust mite-containing Viaskin or Finn chamber patches were applied to the thoracic skin of six mite-hypersensitive Maltese-beagle crossbred atopic dogs. Lesions were graded 49 and 72 h after patch test application, and skin biopsies were collected after 72 h. Overall microscopic inflammation, eosinophil and T-lymphocyte infiltrations were scored., Results: Positive macroscopic patch test reactions developed at five of six Viaskin application sites and four of six Finn chamber application sites. Median microscopic epidermal and dermal inflammation, as well as eosinophil and CD3 T-lymphocyte dermal scores were always higher in biopsies collected at Viaskin than at Finn chamber sites. Microscopic inflammation scores were significantly higher after mite allergen-containing Viaskin compared with empty patches, but this was not the case for mite-containing Finn chambers compared with control chambers. Scores obtained using Viaskin were not significantly different from those obtained using Finn chambers. Macroscopic and microscopic scores were significantly correlated., Conclusions and Clinical Importance: In mite-allergic dogs, Viaskin epicutaneous delivery systems appear to induce stronger allergen-specific inflammation than currently used Finn chamber patch tests. Consequently, Viaskin patches might offer a better alternative for screening cellular hypersensitivity to food and environmental allergens., (© 2012 The Authors. Veterinary Dermatology © 2012 ESVD and ACVD.)

Discoid lupus erythematosus (DLE) is a common canine autoimmune disease that usually manifests as a localized ulcerative and scarring nasal dermatitis. We report herein a generalized variant of canine DLE successfully treated with the antimalarial immunomodulator hydroxychloroquine (HCQ). A 9-year-old hairless Chinese crested dog was presented with annular and polycyclic hyperpigmented and scaly skin lesions with central erosions, hypopigmentation and/or scarring on the trunk, neck and lateral extremities. Associated systemic signs were not seen. The clinical diagnosis of generalized DLE was supported by the demonstration of lymphocyte-rich interface dermatitis with epidermal atrophy and dermo-epidermal deposition of immunoglobulins and activated complement. As for human DLE, treatment was initiated with HCQ at 5 mg/kg once daily along with 2 weeks of 0.1% tacrolimus ointment and restriction of sun exposure. Over the following year, complete remission was maintained with HCQ at 5 mg/kg orally once daily with the exception of three relapses; two occurred during treatment induction and the third arose when the frequency of HCQ administration was reduced to every other day. Disease flares were controlled with 0.1% tacrolimus ointment alternating with 0.1% prednicarbate cream once daily for 5-10 days. Altogether, adverse drug events were not seen with this regimen. In summary, clinically, histologically and immunologically, this dog's disease mirrored the generalized discoid variant of chronic cutaneous lupus erythematosus of humans. The apparent benefit of HCQ, its safety and low cost warrant future investigations of its use for treatment of canine cutaneous lupus variants., (© 2011 The Authors. Veterinary Dermatology © 2011 ESVD and ACVD.)

Promeris Duo (PD) is a novel topical flea and tick preventative for dogs, which is also licensed for treatment of canine demodicosis. In this article, we present 22 dogs that all developed pemphigus foliaceus (PF)-like cutaneous drug reactions at the site of PD application. In eight dogs, the lesions were restricted to the application site (localized group). Signs of systemic illness were reported in three dogs, and four required immunosuppressive treatment. Direct immunofluorescence for IgG was positive in four dogs, although circulating antikeratinocyte IgG could not be detected in any tested sera. Complete remission was achieved in all dogs, with one patient still remaining on treatment. Fourteen dogs developed skin lesions at the application site as well as other noncontiguous areas (distant group). Systemic signs were reported in 11 dogs, and immunosuppression was required in 10 cases. Direct and indirect immunofluorescence tests were positive for antikeratinocyte autoantibodies in 10 of 13 and six of 10 patients with distant disease, respectively. Complete remission was achieved in 10 of 13 dogs with distant disease; one-third are still on treatment. Histological changes were similar to canine PF. Desmosomal architectural changes, assessed by desmoglein-1 immunostaining, were also similar to those of dogs with spontaneous autoimmune PF. Apoptosis did not appear to contribute to lesion formation, in either autoimmune or PD-associated PF. In conclusion, PD has the potential of triggering a variant of PF that resembles spontaneously occurring autoimmune PF at clinical, morphological, immunological and treatment outcome levels., (© 2011 The Authors. Veterinary Dermatology. © 2011 ESVD and ACVD.)

Pemphigus foliaceus (PF) is the most common canine autoimmune skin disease. In contrast to human PF (hPF), desmoglein-1 is a minor autoantigen in the canine disease. The major autoantigen(s) of canine PF (cPF) remain(s) unknown, which limits the ability to perform mechanistic studies of lesion formation and the development of novel diagnostic and therapeutic strategies for this disease. The immunofluorescence patterns of selected desmosomal (desmoglein-1, desmoglein-3, desmocollin-1, desmocollin-3, desmoplakin-1/2, plakoglobin and plakophilin-1) and nondesmosomal adhesion proteins (E-cadherin, claudin-1, zona occludens-1 and occludin) in healthy canine footpad, haired skin and buccal mucosal epithelia were determined using hPF and pemphigus vulgaris sera and specific antibodies. The immunostaining patterns were then compared with that of indirect immunofluorescence staining with 66 cPF sera. Most cPF sera (58 of 66; 88%) exhibited positive staining along keratinocyte margins in the stratum spinosum and stratum granulosum of canine footpad. One serum contained autoantibodies binding solely to stratum granulosum keratinocytes. Concurrent intercellular fluorescence in the stratum basale was limited to seven of 66 cPF sera (11%). Only 12 of 66 cPF sera (18%) also exhibited positive IF staining of the buccal mucosa. This study confirms the immunological heterogeneity of cPF immunoglobulin G autoantibodies. Moreover, the major indirect immunofluorescence staining pattern and the inability of most cPF sera to label the buccal mucosa closely matched that of desmocollin-1. These observations warrant further investigation of desmocollin-1 as a potential major cPF autoantigen., (© 2010 The Authors. Journal compilation © 2010 ESVD and ACVD.)

Necrolytic migratory erythema (NME; also known as superficial necrolytic dermatitis) is a syndrome most often associated with certain chronic liver diseases or pancreatic glucagonomas. In humans with glucagonoma-associated NME, skin lesions usually respond to octreotide, a somatostatin analogue that inhibits glucagon release. In this report an 11-year-old golden retriever dog with pancreatic glucagonoma and metastasis to the regional lymph nodes, spleen and liver was diagnosed with NME. The dog exhibited erosions, ulcers and crusts on the paws, pressure points, muzzle, periocular area and prepuce. The dog was also anorexic and had difficulty walking. Because metastasis precluded surgery, treatment was initiated with subcutaneous octreotide (2 μg/kg twice daily). Skin lesions and systemic clinical signs improved markedly within 5 days. The dosage was increased to nearly 3 μg/kg twice daily and signs almost completely resolved within 10 days. Anorexia was the major adverse effect observed. During the following month, both dosage (1-3.7 μg/kg) and frequency (two to four times daily) of the octreotide injections were adjusted to permit control of clinical signs while maintaining adequate appetite. Temporary cessation of octreotide administration resulted in the rapid recurrence of skin lesions. Resuming injections led to improvement of clinical signs within 48 h. The dog was later euthanized because of progressive metastatic disease. In conclusion, subcutaneous octreotide injections were beneficial in this dog with glucagonoma-associated NME. This somatostatin analogue could be a valuable option to treat canine patients with non-resectable or relapsing pancreatic glucagonoma-associated NME., (© 2010 The Authors. Journal compilation © 2010 ESVD and ACVD.)

The inhibitory effect of 0.0584% hydrocortisone aceponate spray on immediate- and late-phase skin reactions and the duration of inhibition after medication withdrawal were studied in 10 Maltese-beagle atopic dogs. All subjects were sprayed on axillary and inguinal regions and on one randomly chosen side of the thorax once daily for 14 (phase 1) or 7 days (phase 2). Intradermal injections (IDT) of histamine and anticanine IgE antiserum were performed bilaterally on the thorax before, 7 and 14 days after treatment. During phase 2, IDT was performed once weekly for 5 weeks. Each IDT was evaluated by an investigator blinded to the site of active treatment. Skin biopsies of 24-h anti-IgE-associated late-phase reactions were collected from both thoracic sides before and 14 days after treatment to determine the number of inflammatory cells and dermal thickness. Phase 1: Histamine and anti-IgE-induced global wheal scores at treated sites were significantly lower after 7 and 14 days with negative reactions present in >90% of dogs. Late-phase reactions at both sides were also significantly decreased compared with that at baseline, and this was associated with reduced inflammatory cell influx. Moreover, a significant decrease in dermal thickness was recorded at treated sides after 14 days. Phase 2: Histamine reactions became positive at untreated sides in all dogs 2 weeks after treatment. In conclusion, the 0.0584% hydrocortisone aceponate spray significantly decreased immediate- and late-phase IDT reactions, and prolonged application caused skin atrophy at treated sites. A 2-week withdrawal period prior to IDT is proposed.

Failure of desmosomal adhesion with ensuing keratinocyte separation - a phenomenon called acantholysis - can result from genetic, autoimmune or infectious proteolytic causes. Rare hereditary disorders of desmosomal formation have been identified in animals. Familial acantholysis of Angus calves and hereditary suprabasal acantholytic mechanobullous dermatosis of buffaloes appear to be similar to acantholytic epidermolysis bullosa of human beings. A genetic acantholytic dermatosis resembling human Darier disease has been rarely recognized in dogs. In autoimmune blistering dermatoses, circulating autoantibodies bind to the extracellular segments of desmosomal proteins and induce acantholysis. Autoantibodies against desmoglein-3 are found in canine pemphigus vulgaris and paraneoplastic pemphigus. Autoantibodies against desmoglein-1 have been rarely detected in dogs with pemphigus foliaceus. When circulating autoantibodies target desmogleins-1 and -3, mucocutaneous pemphigus vulgaris develops in dogs. Finally, several infectious agents can release proteases that cleave desmosomal bonds. In superficial pustular dermatophytosis of dogs and horses, Trichophyton hyphae colonize the stratum corneum, and acantholysis presumably develops because of proteases secreted by the dermatophytes. In exudative epidermitis of piglets, Staphylococcus bacteria - usually Staphylococcus hyicus- release exfoliatin toxins that bind to and specifically cleave desmoglein-1. Any of the above mechanisms can result in impairment of desmosomal function with subsequent acantholysis. The end point of adhesion failure is identical among these diseases: there is cleft formation where desmosomes are affected. The similarity of mechanisms explains why clinical and microscopic skin lesions overlap between entities, thus leaving clinicians and dermatopathologists with the conundrum of determining whether the acantholysis is of genetic, autoimmune or infectious origin.

The broad spectrum of clinical signs in canine cutaneous epitheliotropic T-cell lymphoma mimics many inflammatory skin diseases and is a diagnostic challenge. A 13-year-old-male castrated golden retriever crossbred dog presented with multifocal flaccid bullae evolving into deep erosions. A shearing force applied to the skin at the periphery of the erosions caused the epidermis to further slide off the dermis suggesting intraepidermal or subepidermal separation. Systemic signs consisted of profound weight loss and marked respiratory distress. Histologically, the superficial and deep dermis were infiltrated by large, CD3-positive neoplastic lymphocytes and mild epitheliotropism involved the deep epidermis, hair follicle walls and epitrichial sweat glands. There was partial loss of the stratum basale. Bullous lesions consisted of large dermoepidermal and intraepidermal clefts that contained loose accumulations of neutrophils mixed with fewer neoplastic cells in proteinaceous fluid. The lifted epidermis was often devitalized and bordered by hydropic degeneration and partial epidermal collapse. Similar neoplastic lymphocytes formed small masses in the lungs associated with broncho-invasion. Clonal rearrangement analysis of antigen receptor genes in samples from skin and lung lesions using primers specific for canine T-cell receptor gamma (TCRgamma) produced a single-sized amplicon of identical sequence, indicating that both lesions resulted from the expansion of the same neoplastic T-cell population. Macroscopic vesiculobullous lesions with devitalization of the lesional epidermis should be included in the broad spectrum of clinical signs presented by canine cutaneous epitheliotropic T-cell lymphoma.

Arteriovenous fistulae (AVF) are defined as congenital or acquired abnormal direct communications between an artery and a vein leading to abnormal blood circulation. This report describes an unusual manifestation of acquired peripheral AVF in a cat for which the diagnosis was confirmed by computed tomographic (CT) imaging and three-dimensional (3D) reconstruction. A 10-year-old female spayed domestic shorthaired cat was presented with a 2-month history of nonhealing, crusting, erosive and ulcerative skin lesions on the dorsal right forepaw. Severe chewing and biting, but not lameness, had been reported. Systemic abnormalities were not noted. Histopathology revealed increased numbers of thin-walled and slightly grouped vascular profiles in the superficial and mid-dermis, which were often markedly dilated and partially obscured by prominent hyaline deposits. There were a few pyknotic nuclear fragments and haemorrhages in vascular walls as well as multifocal luminal thrombosis with or without recanalization. Differential diagnoses included progressive angiomatosis with trauma or AVF with secondary regional venous hypertension. Computed tomographic images were acquired using a 16-slice Siemens Somotom Sensation CT scanner, and 3D images were created using the Voxar 3D software. Image reconstruction revealed tortuous aberrant vasculature on the medial aspect of the radius and around the carpus compared to normal vascularization on the contralateral limb. These changes were suggestive of the diagnosis of acquired peripheral AVF. The differential diagnosis for localized, nonhealing, haemorrhagic, crusted, erosive or ulcerative distal extremity skin lesions in cats should include acquired AVF, and diagnosis may be confirmed with contrast-enhanced CT imaging.