Thymoma-associated exfoliative dermatitis in cats

Five cases of exfoliative dermatitis in cats were presented from 1996 to 2002 in which a feline thymoma was found by postmortem or postsurgical examination. Besides abundant exfoliation of keratin squames and layers, the histologic picture of the skin revealed a similar pattern of interface dermatitis with predominantly CD3+ lymphocytes and fewer mast cells and plasma cells. In the epidermal basal layer a hydropic degeneration of keratinocytes was present. In all cases an infundibular lymphocytic mural folliculitis and absence of or drastic decrease in the number of sebaceous glands occurred. In addition to the so far described cell-poor type, we also found examples of a cell-rich skin lesion. Together with the clinical observation of generalized exfoliative dermatitis, the histologic pattern of this dermatitis was suggestive of an underlying thymoma. The pathogenesis of this skin disease in association with thymic neoplasia remains obscure, and our results contradict the hypothesis of production of autoantibodies that cross-react with epithelial antigens. The morphology of the thymomas and CD3 expression of the thymocytes varied and did not seem to have an impact on the dermal lesions.     

Thymoma-associated exfoliative dermatitis in a rabbit

A 5-year-old rabbit with generalized scaling is presented. Multiple skin scrapings and acetate tape impressions were negative for mites and Malassezia. Culture for dermatophytes was also negative. Skin biopsies showed similarities with sebaceous adenitis described in rabbits (absence of sebaceous glands, perifollicular lymphocytic infiltrate at the level of the absent sebaceous glands, lymphocytic mural folliculitis, interface dermatitis). The owners refused any treatment and 2 months later the rabbit was euthanized due to anorexia. At necropsy a mass was found in the anterior mediastinum. Histopathology confirmed a diagnosis of thymoma. A possible paraneoplastic skin disease was suspected, based on similarities with thymoma-associated exfoliative dermatitis in cats.     

Equine herpesvirus 1‐associated ulcerative dermatitis in a horse

This case report describes the clinical and histopathological findings of an infection caused by equine herpesvirus‐1 (EHV‐1) in a horse showing respiratory signs and a papular, crusted and ulcerative dermatitis involving mucosae. This diagnosis was supported by real‐time PCR positive for EHV‐1 on nasal swabs and tissues.     

Thymoma-associated exfoliative dermatitis with post-thymectomy myasthenia gravis in a cat

Thymoma-associated exfoliative dermatitis was suspected in a cat with a cranial mediastinal mass. The dermatopathy resolved with surgical removal of a thymoma. The cat manifested neurologic signs consistent with myasthenia gravis 7 wk after surgery. Exfoliative dermatitis and post-thymectomy myasthenia gravis in the same cat has not been reported previously.     

A seasonal eosinophilic dermatitis in cats

Twenty cats from Nelson with distinctive crusting and erosive dermatitis of the nasal bridge and histological lesions of eosinophilic dermatitis, often with collagenolysis, were examined in 1990 and 1991. Four of the cats also had pinnal dermatitis and five had eruptive lesions on the chin. The condition was intermittent and seasonal, occurring in summer and autumn. It is probable that the lesions were caused by hypersensitivity to insect bites, as has been demonstrated in a similar clinicopathological syndrome recently recognised in Australia.     

Ulcerative facial and nasal dermatitis and stomatitis in cats associated with feline herpesvirus 1

Ulcerative dermatitis of the nasal planum or haired skin of the face, associated with intranuclear inclusion bodies compatible with herpesvirus, was identified in nine cats. Clinically, lesions were ulcerative and crusted, and often persistent. A tenth cat had focal proliferative ulcerative stomatitis, also associated with intranuclear inclusion bodies. Microscopically, there was necrosis and ulceration associated with prominent eosinophilic inflammation. Intranuclear inclusion bodies were noted in all cases, within the surface or adnexal epithelium. Ultrastructural examination of skin from two cats revealed virions morphologically compatible with a herpesvirus. Polymerase chain reaction (PCR) specific for feline herpesvirus 1 on DNA extracted from fresh-frozen or formalin-fixed paraffin-embedded biopsy samples and/or consensus primer PCR with DNA sequencing performed on DNA extracted from formalin-fixed paraffin-embedded biopsy samples from seven cats revealed that the virus was indistinguishable from feline herpesvirus 1. PCR was negative in one of eight cats tested.     

Diagnostic value of exfoliative cytology of body fluids in dogs and cats

A method for collecting body fluids for cytological examination and their subsequent preparation and staining is described. The results of the cytological examination of 80 dogs and 26 cats over a period of three years are reported, indicating the number and types of condition which can be diagnosed, together with the clinicopathological correlations.     

Mosquito bite-caused eosinophilic dermatitis in cats.

Eight cats had lesions on the nasal bridge, ears, and footpads, with histologic and hematologic features of a recently described seasonal form of eosinophilic granuloma complex. Four cats were examined in detail, and it was established that 2 of the 4 reacted to mosquito extract on intradermal skin testing read at 20 minutes. Neither of the 2 cats tested had deposits of immunoglobulins in lesional or perilesional skin. Lesions on all 4 cats resolved when kept at home behind insect screening, but flared up if the screening was removed. Mosquitoes that were observed to be biting and causing lesions were collected and identified. Other species of laboratory-reared mosquitoes were allowed to bite nonlesional skin of 1 affected cat, causing pruritus, erythematous crusting, and ulcerative lesions at the bite site, which was characterized histologically as eosinophilic dermatitis.     

Comorbidity of ectopic thymoma-associated exfoliative dermatitis and pemphigus foliaceus in a cat

An 8-year-old cat was presented with pruritus, purulent paronychia, scaling, crusting, and spontaneous alopecia. Histopathology revealed intraepidermal neutrophilic pustular acantholytic dermatitis and hyperkeratotic cytotoxic interface dermatitis. No thoracic mass was seen on a lateral radiograph. Ectopic thymoma was discovered on necropsy. This case highlights the necessity for thorough investigation of any case of feline exfoliative dermatitis and pemphigus foliaceus for the presence of thymoma.Key clinical message:Comorbidity of exfoliative dermatitis and pemphigus foliaceus in a cat should prompt a thorough investigation for presence of a thymoma, possibly with advanced imaging techniques.     

Cellular immunophenotyping of exfoliative dermatitis in canine leishmaniosis (Leishmania infantum)

Lymphocyte subsets, major histocompatibility complex (MHC)-II expressing cells and number of amastigotes in the epidermis and dermis were investigated immunohistochemically in 48 dogs with patent leishmaniosis, with or without exfoliative dermatitis (ED) to study the immunopathogenesis of this common cutaneous form of the disease. Skin biopsies were obtained and compared for ED sites (group A, n = 26), normal-appearing skin from the same animals (group B, n = 24), and leishmanial dogs not exhibiting ED (group C, n = 22), and normal controls (group D, n = 22). The CD3+, CD45RA+, CD4+, CD8+ (CD8a+), CD21+, and MHC-II+ cells and leishmania amastigotes were identified immunohistochemically and counted with the aid of an image analysis system. Pyogranulomatous to granulomatous dermatitis, expressed in various histopathological patterns, was noticed in all groups A and B and in half of group C dogs. In the epidermis, the low number of T-cells and their subsets did not differ significantly between groups A and B, but CD8+ outnumbered CD4+ lymphocytes in both groups. MHC-II+ expression on epidermal keratinocytes was intense in the skin with and without lesions from dogs with ED but not in group C dogs. CD3+, CD8+ and MHC-II+ cells were fewer in group C compared to group A and B dogs. In the dermis, CD3+ cells in group A animals were mainly represented by the CD8+. CD45RA+ and CD21+ cells were also seen in high numbers. MHC-II expression, potentially in lymphocytes, fibroblasts, dendritic cells, and macrophages was intense. The numbers of all cellular subpopulations in the dermis were significantly different between the groups, being highest in group A and lowest in group D. In sebaceous adenitis sites, CD4+ outnumbered CD8+ cells in contrast to the neighbouring dermis and the epidermis. The number of CD21+ and CD45RA+ cells was much lower in the inflamed sebaceous glands compared to the dermis. Finally, the number of amastigotes in the normal-appearing skin was significantly higher in the ED dogs (group B) than in those not exhibiting this cutaneous form of the disease (group C).     

Herpesvirus dermatitis in two cats without facial lesions

Background – Cats with feline herpesvirus (FeHV‐1)‐associated dermatitis typically present with ulcerative lesions on the rostral muzzle and nasal planum. This report describes FeHV‐1 dermatitis in the flank region, in the absence of facial lesions. Hypothesis/Objectives – Clinicians should be aware of this unusual manifestation of FeHV‐1 dermatitis to prevent potential misdiagnosis. Animals – A 12‐year‐old male castrated Bengal cat and a 3‐year‐old male castrated Siamese cat with plaques and ulcers in the flank region are described. Methods – Formalin‐fixed biopsy samples were obtained from lesional skin. Histopathology and FeHV‐1 immunohistochemistry were performed. Results – Each sample had epidermal and follicular necrosis with a dense dermal infiltrate of eosinophils. Few to moderate numbers of intranuclear inclusion bodies were present in keratinocytes. The presence of FeHV‐1 in the lesions was confirmed with immunohistochemistry. Conclusions and clinical importance – Feline herpesvirus‐associated dermatitis should not be ruled out based on the location of the lesion, because a correct diagnosis is imperative for proper treatment. Future studies to assess the cause of lesions at this unusual site are warranted.     

Chiari‐like malformation in two cats

Two male, neutered, domestic, shorthaired cats were evaluated for progressive paresis and ataxia. Neurological examinations suggested a spinal cord lesion in each case. Complete blood examination and cerebrospinal fluid analysis were unremarkable in both cats. MRI revealed malformation of the occipital bone with herniation of the cerebellar vermis through the foramen magnum but without syringomyelia. Chiari‐like malformation was suspected in both patients. MRI repeated one year later in both cats because of progression of clinical signs yielded the same findings as the initial scans. Foramen magnum decompression in one cat was associated with resolution of clinical signs.