Mycobacterial dermatitis.

Mycobacterial skin disease in cats associated with atypical mycobacteria is an uncommon disease in small animal practice, and the disease is rarely encountered in dogs. A mycobacterial etiology should be considered in cases of chronic nodular dermatitis, draining tracts, and panniculitis. Cats and dogs affected with atypical mycobacterial infections are usually otherwise healthy, and systemic illness is unusual. In most cases, a diagnosis is made based on histopathological findings and growth of a causative organism. Group IV atypical mycobacteria can usually be grown following submission of affected tissue. Treatment should be based on antibiotic sensitivity test results. Treatment is prolonged and is unsuccessful in many cases. In cases of feline leprosy and canine leproid granuloma syndrome, organisms are difficult if not impossible to grow, and clinical and histopathological findings should be used to make a diagnosis. Spontaneous resolution of disease has been reported in atypical mycobacteriosis, feline leprosy, and canine leproid granuloma syndrome.     

Malassezia dermatitis and otitis.

The incidence of dermatitis and otitis resulting from overgrowth of M. pachydermatis is great enough that cytological sampling techniques should be considered a routine part of the dermatological examination. Because most cases of MD and Malassezia otitis cannot be grossly distinguished from bacterial pyoderma and otitis, respectively, efficiency in performing cytology testing of skin and ear canal exudate is essential to the successful diagnosis and management of pruritic skin diseases and otitis. Although Malassezia infections are rarely primary, therapy can be instituted to remove the yeast as a confounding factor while a differential diagnosis is pursued in evaluating the underlying disease process.     

Fungal dermatitis in captive pinnipeds.

Fungal dermatitis was diagnosed in two captive gray seals (Halichoerus grypus) and four harbor seals (Phoca vitulina) between 1992 and 1994. Trichophyton mentagrophytes, Malassezia spp., and Yarrowia (Candida) lipolytica were isolated. Erythematous, thickened, alopecic skin lesions were present on the face and on the flippers, particularly around the nail bed. The two most important environmental factors associated with development of fungal dermatitis appeared to be excessive chlorination of pool water and warm water temperature.     

Sterile nodular dermatitis in dogs.

The types of canine sterile nodular dermatitis discussed in this article have in common the clinical presentation of nodules or plaques; however, they differ in many aspects such as breed predilection, distribution and evolution of cutaneous lesions, systemic involvement, response to therapy, and prognosis. The definitive diagnosis should be based on multiple skin biopsy results. Other ancillary tests may be indicated in cases of systemic involvement. In addition, serum alpha1 antitrypsin can be measured to demonstrate the association between nodular panniculitis and serum alpha1 antitrypsin deficiency. A better understanding of the etiopathogenesis of each of these interesting skin conditions necessitates extensive and systematic diagnostic approaches.     

Allergic contact dermatitis in the dog. Principles and diagnosis

Allergic contact dermatitis is a rare hypersensitivity disorder in the dog. Clinical diagnosis is not easy. Primary lesions are transient. Secondary lesions caused by chronic inflammation and self-trauma are commonly present on typical areas, especially in sparsely haired regions and on the feet. A presumptive diagnosis can be made based on the history, clinical signs, and positive standardized closed patch testing. Histopathology and basophil degranulation testing may also be helpful in supporting the diagnosis and in identifying the offending allergens. However, a definitive diagnosis can be made only after restriction-provocation testing. With better understanding of the pathogenesis and clinical signs, and with increased availability of diagnostic tests (especially a standardized closed patch test), increased recognition of this dermatosis is expected.     

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.     

The ACVD task force on canine atopic dermatitis (III): the role of antibodies in canine atopic dermatitis.

Although an important pathogenic role for IgE is established in the case of allergic asthma and rhinitis in man, its role in atopic dermatitis is less clear. There are many studies where allergists and immunologists have provided evidence in favour of such a role, whereas dermatologists are less than convinced.In dogs, however, there is an abundance of clinical evidence implying that atopic dermatitis is antigen driven, and recent studies suggest that there may be a role for IgE, not only in the effector pathway, but also in antigen capture. Although an IgG response often accompanies an IgE response in dogs with atopic dermatitis, there is little evidence in support of a pathogenic role in respect of the former isotype.