CHAPTER 5 – The Skin and Appendages

Resume— Cette etude decrit les modelites reactionnelles inflammatoires et l'immunophenotype des lesions histologiques de demodecie canine. Trois modalites principales sont decrites: une folliculite parietale, une folliculite suppurative et furonculose, et une dermatite modulaire. La folliculite parietale, reaction inflammatoire ciblee sur la paroi folliculaire, est presente dans tous les cas et constitue la modalite reactionnelle principale dans 17 cas sur 34 (50 pour cent). Le sous-type interface, caracterise par une degenerescence hydropique ou une apoptose des keratinocytes folliculaires, avec exocytose lymphocytaire, s'observe dans 15 de ces 17 cas. Une melanose folliculaire et/ou une incontinence pigmentaire sont presentes sur 10 de ces 17 biopsies. Une dermatite nodulaire, representee par un granulome perifolliculaire, est presente sur neur biopsies (26 pour cent). Une folliculite suppurative ou une furonculose est la modalite relationnelle dominante dans huit cas (24 pour cent). Tous les lymphocytes dans la paroi folliculaire sont des lymphocytes T CD3+, contre 10 pour cent sculement des cellules perifolluculaires. Les plasmocytes IgG+ constituent jusqu'a 74 pour cent des cellules perifolliculaires, et le pourcentage est encore plus eleve dans les cas de furonculose. Ces faits montrent que la folliculite parietale est une lesion importante dans la demodecie canine, et suggere qu'une reaction a mediation cellulaire est dirigee specifiquement contre la paroi folliculaire. [Canine demodicosis: a re-examination of the histopathologic lesions and description of the immunophenotype of infiltrating cells (La demodecie canine: reexamen des lesions histologiques et description de l'inmunophenotype des cellules infiltrantes).



Resumen— Este estudio describe los patrones inflamatorios y el immunofenotipo de las lesiones histologicas en la demodicosis canina. Se identificaron tres patrones principales: foliculitis mural, foliculitis y furunculosis supurative, y dermatitis nodular. La foliculitis mural, una reaccion inflatatoria dirigida a la pared folicular, se observo en todos los casos y constituia el patron principal en 17 de los 34 casos (50%). En 15 de estos 17 casos la foliculitis mural era de tipo interfase, caracterizada por degeneracion hidropica o apoptosis de queratinocitos foliculares y exocitosis linfocitica. Se detecto melanosis folicular y/o incontinecia pigmentaria en 10 de estas 17 biopsias. Neuve biopsias (26 por ciento) presentaban dermatitis nodular, caracterizada por granulomas perifoliculares. Ocho casos (24 por ciento) mostraban foliculitis o furunculosis como patron dominante. Linfocitos T CD3+ constituian la totalidad del infiltrado en la pared folicular, mientras que el mismo tipo celular representaban el 10 por ciento del infiltrado inflamatorio perifolicular. Hasta el 74 por ciento de las celulas perifoliculares eran celulas plasmaticas IgG+, con el mayor numero en casos con furunculosis. Estos hallaz os indican que la foliculitis mural es una lesion importante la demodicosis canina y sugiere que una reaccion mediada por celulas es dirigida a la pared folicular. [Canine demodicosis: a re-examination of the histopathological lesions and description of the immunophenotype of infiltrating cells (Demodicosis canina: repaso de las lesiones histopatologicas y descripcion del inmunofenotipo del infiltrado celular).



Abstract— This study describes the inflammatory patterns and immunophenotype of the histologic lesions of canine demodicosis. Three major patterns were identified: mural folliculitis, suppurative folliculitis and furunculosis and nodular dermatitis. Mural folliculitis, an inflammatory reaction targeting the follicular wall, was seen in all cases and was the principle pattern in 17 of 34 cases (50 per cent). The interface subtype of mural folliculitis, typified by hydropic degeneration or apoptosis of follicular keratinocytes and lymphocytic exocytosis, occurred in 15 of these 17 cases. Follicular melanosis and/or pigmentary incontinence occurred in 10 of these 17 biopsies. Nodular dermatitis, represented by perifollicular granulomas, was present in nine biopsies (26 per cent). Suppurative folliculitis or furunculosis was the dominant pattern in eight cases (24 per cent). All lymphocytes within the follicular wall were CD3+ T lymphocytes, compared to 10 per cent of the perifollicular cells. IgG+ plasma cells accounted for up to 74 per cent of perifollicular cells, highest in cases with furunculosis. These findings indicate that mural folliculitis is an important lesion of canine demodicosis, and suggests that a cell-mediated reaction is targeting the follicular wall.

Canine Demodicosis: A Re-examination of the Histopathologic Lesions and Description of the Immunophenotype of Infiltrating Cells.

The available reports upon the occurrence of mites of the Demodicidae in the cat are reviewed and current knowledge of the biology is discussed. The conclusion is drawn that demodicosis of the cat is more prevalent than previously supposed. It is found in both male and female, in long- and shorthaired coat types, and in several breeds. Infestation may be found in the absence of frank signs, or it may be associated with systemic diseases. However, it remains unclear whether the parasite can itself cause clinically apparent disease.

Demodicosis in the cat

An immunohistochemical study of the lesions of demodicosis in the dog.

The skin is the largest organ of the body with many different functions as thermoregulation, immune protection, sensory perception, vitamin D production and it acts as a barrier be‐ tween the animal and the environment. Besides all of these important functions and the dis‐ eases that affect directly the skin, it may also share or reflect pathologic processes from other tissues. Due to these characteristics, dermatologic problems are among the most commonly seen disorders in veterinary hospitals. It is important for the veterinarian to know and un‐ derstand about the physiology of the skin and about the most common dermatologic disor‐ ders that affects dogs and cats, which will be addressed in this chapter.

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K.P. Baker

Papers

The histopathology and pathogenesis of demodecosis of the dog.