Mastocytosis in the skin in dogs: A multicentric case series.

Canine cutaneous mastocytosis (CM) is rare in contrast to canine mast cell tumours. In humans, CM commonly affects children and is usually indolent with possible spontaneous resolution. Systemic mastocytosis (SM) with bone marrow involvement typically affects adults, can have a poor outcome, and often includes skin lesions. 'Mastocytosis in the skin' (MIS) is the preferred term of skin lesions, if bone marrow evaluations are not available, which is often the cases in dogs. In human SM and CM, KIT mutations are often detected. The veterinary literature suggests clinical resemblances between human and canine MIS, but data is limited, and KIT mutations are rarely assessed. This retrospective study describes clinicopathological findings, treatment and outcome of 11 dogs with suspected MIS. Dogs with multiple mast cell tumours were excluded. Histopathology reports (n = 5) or slides (n = 6) were reviewed. KIT mutation analysis including exons 8, 9, 11, 14 and 17 were analysed in eight dogs. Median age at diagnosis was 4 years (range, 1-12). Typical clinical signs included multifocal to generalised nodules and papules. Histologically, skin lesions were characterised by dermal infiltration of well-differentiated mast cells. KIT mutations were detected in 3/8 dogs (exon 9: n = 2; exon 11: n = 1). One dog had mastocytaemia suggesting possible SM. Glucocorticoids were mostly successful with lesion improvement in all treated dogs (n = 8). This cohort highlights resemblances between human and canine MIS. Further studies are required to confirm these findings and establish diagnostic criteria for CM and MIS associated with SM in dogs.

Characterization of the serum and skin inflammatory profile in canine pemphigus foliaceus using multiplex assay and quantitative real-time polymerase chain reaction (qRT-PCR).

Canine pemphigus foliaceus (PF) is a common autoimmune skin disease characterized by autoantibodies binding to epithelial adhesion molecules resulting inflammatory response. The immune network of cytokine and chemokine abnormalities that characterize the immune response in canine PF are poorly explored. This study evaluated serum and lesional skin cytokine and chemokine profiles of dogs diagnosed with PF compared to healthy control dogs. Serum samples obtained from 11 PF dogs and 16 healthy control dogs were analyzed using commercially available canine multiplex assay for 13 biomarkers (Canine Milliplex assay). Eight lesional skin samples from seven PF dogs and five healthy site-matched samples from five healthy dogs were evaluated for 20 immune markers using quantitative real-time PCR. Immunomodulating medications were suspended for at least four weeks in all dogs before obtaining serum and skin samples. PF patients showed significantly higher serum concentrations of tumor necrosis factor-α, interleukin (IL)- 6, IL-8, IL-18, CCL2, KC-like, and granulocyte-macrophages colony-stimulating factor when compared to healthy controls (Mann-Whitney U test; p < 0.05 for all). Lesional PF skin exhibited significant expression and upregulation of pro-inflammatory/T helper (Th1) 1 markers IL-1ß, MX1, GZMB, OAS1, and IFN-γ as well as Th2 cytokines IL-13, IL-33, TSLP, IL-31 and Th17/22 markers IL-17A and IL-22 (Mann-Whitney U test; p < 0.05 for all). Taken together, the findings from this study describe the role of numerous cytokines and chemokines associated with immune response in the skin and serum of canine PF patients. Further larger-sample proteomics and RNA-sequencing transcriptomics studies are needed to understand the immune pathogenesis of canine PF skin lesions.

Transcriptome analysis of selected cytokine and chemokines in the eosinophilic plaques of cats with atopic skin syndrome.

BACKGROUND: Previous evaluations of cytokine and chemokine gene expressions [messenger (m)RNA] in the skin of allergic cats were mostly unsuccessful in detecting the T-helper 2 (Th2) pathway, which is associated with the major effector cytokines interleukin (IL)-4, IL-5 and IL-13. HYPOTHESIS/OBJECTIVE: To evaluate differences in the mRNA expression in eosinophilic plaques of cats diagnosed with feline atopic skin syndrome (FASS) compared to healthy controls. ANIMALS: Four client-owned cats with FASS with eosinophilic plaques and five healthy control cats. MATERIALS AND METHODS: Gene expressions (mRNA) of 14 cytokines and chemokines from eosinophilic plaque skin of cats with FASS and site-matched skin samples from healthy controls were analysed using quantitative reverse-transcription PCR analysis. RESULTS: Eosinophilic plaques were characterized by upregulation of Th2 cytokines IL-4 (p ≤ 0.01), IL-5 (p ≤ 0.01) and IL-13 (p ≤ 0.01) and Th2-attracting chemokine CCL17 (p ≤ 0.05). Moreover, there was higher expression of S100 calcium-binding protein A 8 (p ≤ 0.01) as well as C-X-C Motif chemokine ligand 10 (CXCL10; p ≤ 0.01), IL-10 (p ≤ 0.05) and the Th17 cytokine IL-17A (p ≤ 0.01) in lesional skin compared to healthy samples. There was no difference in gene expressions of IL-12A, IL-31, IL-33, thymic stromal lymphopoietin (TSLP), tumour necrosis factor-α (TNF-α) or CCL5. CONCLUSIONS AND CLINICAL RELEVANCE: Results demonstrate that eosinophilic plaques feature dominant Th2 and IL-17A inflammatory responses in the skin. Further larger-sample transcriptome studies are needed to advance our understanding of the pathogenesis of different skin lesions in FASS.

Topical Imiquimod Therapy for Localized Solar Dermatitis in a Dog.

Chronic sun exposure in dogs can result in clinical changes in the skin referred to as solar or actinic dermatitis. A 5-year-old, neutered male, American Bulldog presented with localized unilateral erythematous macules, plaques, alopecia, comedones and hemorrhagic bullae involving the non-pigmented skin on left lateral ventral flank area. The presence of hyperplastic epidermis with keratinocyte dysplasia, superficial dermal elastosis, and multiple follicular cysts with occasional rupture (furunculosis) on histology, together with history and characteristic skin lesions was consistent solar dermatitis/actinic keratosis. Skin scrapings were negative and treatment for secondary pyoderma was initiated with oral clindamycin for 8 weeks. After 2 months of antibiotic therapy, the hemorrhagic bullae resolved; however, erythematous solar/actinic skin lesions with induration and comedones persisted. Topical application of imiquimod 5% cream 3 times weekly for 8 weeks resulted in the resolution of erythema, but some of the non-inflamed comedones remained. Staining for elastin and Ki67 revealed keratinocyte hyperplasia in hair follicle infundibulums and alterations in the elastic fibers around follicles, which may lead to closure and formation of follicular cysts. Imiquimod has been long suggested as a treatment option for solar dermatitis, but this is the first known case report detailing its efficacy in dogs.

NSDHL Frameshift Deletion in a Mixed Breed Dog with Progressive Epidermal Nevi.

Loss-of-function variants in the NSDHL gene have been associated with epidermal nevi in humans with congenital hemidysplasia, ichthyosiform nevi, and limb defects (CHILD) syndrome and in companion animals. The NSDHL gene codes for the NAD(P)-dependent steroid dehydrogenase-like protein, which is involved in cholesterol biosynthesis. In this study, a female Chihuahua cross with a clinical and histological phenotype consistent with progressive epidermal nevi is presented. All exons of the NSDHL candidate gene were amplified by PCR and analyzed by Sanger sequencing. A heterozygous frameshift variant, c.718_722delGAACA, was identified in the affected dog. In lesional skin, the vast majority of NSDHL transcripts lacked the five deleted bases. The variant is predicted to produce a premature stop codon truncating 34% of the encoded protein, p.Glu240Profs*17. The mutant allele was absent from 22 additionally genotyped Chihuahuas, as well as from 647 control dogs of diverse breeds and eight wolves. The available experimental data together with current knowledge about NSDHL variants and their functional impact in humans, dogs, and other species prompted us to classify this variant as pathogenic according to the ACMG guidelines that were previously established for human sequence variants. Therefore, we propose the c.718_722delGAACA variant as causative variant for the observed skin lesions in this dog.

Successful Treatment of Cutaneous Curvularia geniculata, Nocardia niigatensis, and Viral Papillomatosis in a Dog During the Therapeutic Management of Immune-Mediated Hemolytic Anemia.

Opportunistic infections represent a major cause of mortality in immunocompromised patients. Discontinuation or reduction of immunosuppressive medications is recommended with the development of opportunistic infections, which may cause a relapse or worsening of the immune-mediated disease. A 7.5-year-old, spayed female great Dane was diagnosed with immune-mediated hemolytic anemia with initial immunosuppressive therapy consisting of oral prednisone, ciclosporin and mycophenolate mofetil. The patient developed diffuse right forelimb pyogranulomatous fungal dermatitis with deep draining tracts 6 weeks into immunosuppressive treatment with Curvularia geniculata growth. Oral once daily terbinafine and itraconazole were initiated; ciclosporin was immediately discontinued and the mycophenolate mofetil/prednisone doses were reduced. The right forelimb skin lesions resolved after 4 weeks, but the patient presented with a diffuse severe neutrophilic dermatitis on the left forelimb; 16S rRNA sequencing identified Nocardia niigatensis. Cutaneous nocardiosis was treated with oral enrofloxacin and doxycycline; systemic immunosuppressive therapies were continued for immune-mediated hemolytic anemia control. One month later, the left forelimb lesions completely resolved but the patient developed several multifocal, exophytic warts; the clinical features and histopathology were consistent with viral papillomas. Within the following 4 weeks, the patient developed severe diffuse papillomatosis of the left forelimb, which was successfully treated with 2 weeks of every other day topical imiquimod administration. In this case, successful treatment of cutaneous opportunistic bacterial, fungal and viral infection was possible with proper treatment even though the immunosuppressive drug treatments could not be discontinued.

Treatment of exfoliative cutaneous lupus erythematosus in a German shorthaired pointer dog with mycophenolate mofetil.

BACKGROUND: Immune-modulating drugs show limited therapeutic efficacy in canine exfoliative cutaneous lupus erythematosus (ECLE); over half of ECLE dogs are eventually euthanized for their lack of response to therapy. OBJECTIVE: To describe a case of generalized ECLE in a dog in which mycophenolate mofetil (MMF) treatment achieved complete remission. ANIMAL: A 3-year-old, male castrated German shorthaired pointer was presented with a three months history of generalized scaling, erythematous macules and plaques, follicular casts and hypotrichosis affecting the head, trunk, ventrum and medial aspects of all limbs. The dog exhibited lameness and stiff gait. METHODS AND MATERIALS: Complete blood count, serum chemistry profile, urinalysis, serum antinuclear antibody test, histopathological examination and RT-qPCR of skin biopsies. RESULTS: Histologically, skin biopsy specimens revealed lymphocyte-rich interface dermatitis, infundibular interface mural folliculitis and periglandular lymphocytic infiltrate. The absence of systemic signs and unremarkable laboratory tests excluded concurrent systemic lupus erythematosus. Treatment of ECLE was initiated with oral MMF (22 mg/kg, twice daily). Within three weeks of starting MMF therapy, a marked improvement in lameness and a moderate decrease in erythema and scaling was observed. After four months, erythema, scaling and follicular casts had completely resolved, and at the time of writing the dog's ECLE remains in complete remission with twice daily MMF (10 mg/kg). The lesional skin transcriptome revealed predominant T helper 1 (Th1) lymphocytic inflammatory response with strong upregulation of interferon pathway. CONCLUSIONS AND CLINICAL IMPORTANCE: To the best of the authors' knowledge, this is the first reported case of successful treatment of ECLE with MMF as a single-agent therapy.

Lokivetmab therapy for pruritus in a dog with cutaneous mastocytosis.

BACKGROUND: Cutaneous mastocytosis (CM) is a rare disease of dogs characterized by rash, pruritus and proliferation of mast cells in the skin. Oral H1 antihistamines are recommended as the treatment to control pruritus. HYPOTHESIS/OBJECTIVE: To describe the effective treatment of pruritus associated with CM with lokivetmab in one dog. ANIMAL: A 4-year-old, spayed female cross-bred dog presented with severely pruritic, erythematous to pigmented macules and papules involving the ventral abdomen, interdigital skin, perivulval area and both pinnae; the pruritus had been unresponsive to treatment with antihistamines, prednisone and ciclosporin. METHODS AND MATERIALS: Complete blood count and serum biochemistry, abdominal ultrasound, blood smear and skin cytological evaluation, PCR, histopathological and immunohistochemical examination of skin biopsies. RESULTS: Skin cytological evaluation revealed high numbers of uniform, heavily granulated mast cells; histopathological findings showed focal dermal proliferations of well-differentiated, uniform mast cells consistent with a low-grade mast cell tumour (MCT). Clinical staging revealed that the disease was confined to the skin. Mutations of c-kit exon 8 and 11 were not detected. Treatment was initiated with anti-canine-interleukin (IL)-31 monoclonal antibody lokivetmab; antihistamines were continued. The dog's pruritus resolved within seven days and was maintained in remission over 15 months with once monthly lokivetmab injections; the skin lesions improved but did not resolve. CONCLUSION AND CLINICAL IMPORTANCE: Lokivetmab treatment was effective in resolving and maintaining pruritus remission in this dog with widespread cutaneous mast cell disease. Whether CM in dogs represent a separate entity that should be distinguished from a low-grade MCT requires further investigation.

Immunomodulatory in vitro effects of oclacitinib on canine T-cell proliferation and cytokine production.

BACKGROUND: Oclacitinib is a Janus kinase inhibitor used to control pruritus and skin lesions in canine allergic skin disease; its effect on canine T cells is not well-characterized. HYPOTHESIS/OBJECTIVES: To evaluate the impact of oclacitinib on cultured T cells using peripheral blood mononuclear cells from dogs. ANIMALS: Six bluetick coonhounds. METHODS AND MATERIALS: Lymphocyte-enriched cells were incubated with or without the T-cell mitogen concanavalin A (Con A), oclacitinib (0.5, 1 or 10 µM), ciclosporin (200 ng/mL), Con A + oclacitinib 1 µM and Con A + ciclosporin. We assessed both T-cell proliferation and the secretion of cytokines. RESULTS: Ciclosporin and oclacitinib both inhibited the spontaneous proliferation of T cells; this effect was significant only after incubation with oclacitinib at 10 µM. At this concentration, oclacitinib significantly reduced the spontaneous secretion of clonal activator cytokines [interleukin (IL)-2, IL-15], pro-inflammatory cytokines (interferon-gamma (IFN-γ), IL-18) and the regulatory cytokine IL-10; tumour necrosis factor alpha (TNF-α) and IL-6 cytokine production was mildly inhibited. After Con A stimulation, only T cells co-treated with ciclosporin achieved a significant proliferation inhibition and reduction of IL-2, IL-10, IL-15, IL-18, IFN-γ and TNF-α. Surprisingly, oclacitinib at 1 µM (337 ng/mL, corresponding to the oral dosage of 0.4-0.6 mg/kg) did not significantly affect Con A-stimulated T-cell proliferation nor cytokine production (IL-2, IL-10, IL-15, IL-18, IFN-γ and TNF-α). CONCLUSIONS: Although a limited number of dogs were investigated, these preliminary results suggest that oclacitinib appears to have immunosuppressive properties, but only at dosages above those used to treat allergic pruritus in dogs.

Tacrolimus therapy for dermal arteritis of the nasal philtrum refractory to surgery and anti-inflammatory therapy (doxycycline/niacinamide and topical fluocinolone) in a dog.

BACKGROUND: Dermal arteritis of the nasal philtrum is a rarely reported condition commonly affecting large breed dogs. OBJECTIVE: To describe the effective treatment of nasal philtrum arteritis with topical tacrolimus in one dog. ANIMAL: A 9-year-old, intact male German shorthair pointer dog was presented with well-demarcated deep erythematous ulcers targeting exclusively the skin of the nasal philtrum, accompanied by frequent series of haemorrhage. METHODS: Complete blood count, serum chemistry profile, urinalysis, histopathological examination and immunohistochemistry of skin biopsies. RESULTS: The presence of a V-shaped ulcer with subendothelial spindle cell proliferation resulting in stenosis of dermal arteries and arterioles on histological evaluation, together with a well-demarcated deep nasal philtrum ulcer was consistent with arteritis of the nasal philtrum. Treatment was initiated with twice daily oral doxycycline and niacinamide in conjunction with topical fluocinolone cream. Over the course of two years, the lesions progressed with frequent bleeding episodes. A novel surgical approach provided deep resection of all grossly affected tissue; four months later a recurrence of fissures and occasional mild bleeding from the original site was noted and there was no improvement after another two months of oral doxycycline/niacinamide and topical fluocinolone treatment. Topical application of 0.1% tacrolimus twice daily resulted in complete healing of the ulceration and normalization of the epidermis. Over the subsequent 15 months, the dog's lesions remained in remission with topical tacrolimus application twice daily. CONCLUSIONS AND CLINICAL IMPORTANCE: Topical tacrolimus ointment appeared effective at inducing and maintaining lesion remission in this dog with nasal philtrum arteritis.

Mucocutaneous lupus erythematosus in dogs (21 cases).

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.