ABSTRACT
BACKGROUND: Alopecia areata (AA) is suspected to be an autoimmune disease directed preferentially against hair follicles (HF) affecting both humans and various mammalian species. Recently, two rodent models of AA were described, namely the ageing C3H/HeJ mouse and the DEBR rat. Despite several case reports of canine AA in the literature, there has been no systematic assessment of the disease in these companion animals, and it is also not known whether dogs with AA could be useful as an outbred homologue of this disease in humans. OBJECTIVES: To evaluate the clinical, histopathological and immunopathological features of 25 dogs with AA and compare these data with those found in the human disease. PATIENTS/METHODS: Twenty-five client-owned dogs exhibiting macroscopic alopecia with peri- or intrabulbar lymphocytic infiltrates were selected for study. Biopsies and sera were obtained and assessed by histopathology, direct immunofluorescence of immunoreactant deposition, immunohistochemistry for lymphocyte markers, indirect immunofluorescence and immunoblotting analysis of circulating serum IgG, selective immunoprecipitation of HF proteins by serum IgG, and passive transfer of purified canine IgG into naïve C57BL/10 mice. RESULTS: Clinical signs including alopecia, skin hyperpigmentation and leucotrichia usually developed during adulthood and were first seen on the face, followed by the forehead, ears and legs. Spontaneous remission of alopecia occurred in 60% of dogs and regrowing hair shafts were often non-pigmented. Histological examination of skin biopsy specimens revealed peri- and intrabulbar mononuclear cell infiltrates affecting almost exclusively anagen HF. Direct immunofluorescence analysis detected HF-specific IgG in 73% of dogs, while indirect immunofluorescence revealed circulating IgG autoantibodies to the HF inner and outer root sheaths, matrix and precortex. Immunoblotting analysis revealed IgG reactivity to proteins in the 45-60 kDa molecular weight range and with a 200-220 kDa doublet. The latter was identified as trichohyalin by selective immunoprecipitation. Purified HF-reactive IgG, pooled from AA-affected dogs, was injected intradermally to the anagen skin of naïve mice where it was associated with the local retention of HFs in an extended telogen phase in AA-treated skin compared with that seen in controls. CONCLUSIONS: These findings are very similar to those reported for human AA patients; therefore, they support the consideration of dogs with AA as a useful homologue for the study of the pathogenesis of this common autoimmune disease of humans.
Subject(s)
Alopecia Areata/veterinary , Autoimmune Diseases/veterinary , Dog Diseases/pathology , Alopecia Areata/immunology , Alopecia Areata/pathology , Animals , Autoantibodies/blood , Autoimmune Diseases/immunology , Autoimmune Diseases/pathology , Disease Models, Animal , Dog Diseases/immunology , Dogs , Female , Fluorescent Antibody Technique, Direct , Fluorescent Antibody Technique, Indirect , Hair Follicle/immunology , Humans , Immunization, Passive , Immunoglobulin G/blood , Immunophenotyping , Male , Mice , Mice, Inbred C57BLABSTRACT
A retrospective study of 125 cutaneous cystic lesions in cats from 1978 to 1987 Revealed 14 examples of the dilated pore of Winer, a lesion previously described in man and in one cat. Histologically, this lesion appears as a flasklike cystic structure with a wide external opening and laminated keratinaceous content. The cyst is characterized by a thickened wall with numerous, closely apposed rete ridges, either at its base or throughout most of the circumference, with a thinner atrophic wall approaching the os. Clinically, the lesion is a hairless nodule or visible cutaneous defect containing either soft keratinaceous material or, more commonly, projections of horn-like material. In man, the lesion is believed to be either a hamartoma or a benign neoplastic process. Surgical excision is curative.
Subject(s)
Cat Diseases/pathology , Cysts/veterinary , Skin Diseases/veterinary , Skin/pathology , Animals , Cats , Connective Tissue/pathology , Cysts/pathology , Epithelium , Female , Male , Retrospective Studies , Skin Diseases/pathologyABSTRACT
Histologically, multiple wart-like papules or hyperkeratotic plaques on the ear pinnae from 4 dogs were characterized as idiopathic benign lichenoid keratosis. Common histologic features included a discrete lesion of irregular and papillated epidermal hyperplasia with a moderate diffuse lichenoid interface inflammatory infiltrate consisting of lymphocytes and plasma cells. There was also focal hydropic degeneration of the epidermal basal cell layer, pigmentary incontinence, and mixed orthokeratotic and parakeratotic hyperkeratosis. In all 4 dogs, the pinnal lesions were unilateral and asymptomatic. Complete surgical excision was curative.
