Peter J. Ihrke, VMD, DACVD
Certain skin lesions are highly characteristic of specific diseases, 'diagnostic entities' or pathophysiologic phenomena and may be used as clinical markers or strong visual clues. The clinical presentation of some of these lesions comes very close to being pathognomonic. These clinical clues can be used to prioritize our index of suspicion when generating differential diagnoses and this allows us to take diagnostic short-cuts when considering the most appropriate clinical and laboratory diagnostic procedures.
Other somewhat less characteristic lesions may be used as visual markers if the lesions are seen in conjunction with strongly supportive data such as breed, sex or age predilections.
The following will be illustrated:
1. Ventral alopecia of rapid onset in a cat with the exposed skin becoming shiny.
2. A well-demarcated band of erythema, papules or comedones extending from the scrotum to the tip of the prepuce in an intact male dog with skin disease.
3. Darkly colored, greasy or waxy, tightly adherent debris that mats the facial hair in a Persian or Himalayan cat.
4. Severe erosive and ulcerative skin disease where when vesicles or bullae rupture, the lesion formed is larger than the intact vesicle or bullae.
5. Severe erosive and ulcerative skin disease where when vesicles or bullae rupture; the lesion formed is the same size as the intact vesicle or bullae.
6. Large comedo located on the ventral abdomen of a young German shepherd dog.
7. Well-demarcated region of alopecia on the shoulder or dorsal thorax of a toy or miniature poodle or Bichon frise.
8. Adult onset excessively fragile, tissue paper thin skin on a previously normal cat.
9. Focal coalescing loss of pigmentation occurring on the lips, planum nasale or elsewhere on the muzzle in a dog.
10. Gradually enlarging and coalescing lesions affecting the dorsal muzzle of a dog that do not violate the planum nasale.
11. Localized patches of thin, atrophic skin sometimes accompanied by large comedo present on the relatively glabrous skin of the ventral abdomen of a dog.
12. Well-demarcated circular plaques with umbilicated centers especially affecting the medial aspects of the ear pinnae in a dog.
13. Well-demarcated ulcerated nodule or nodules located on the ear pinnae or head of a short-coated dog. Especially in a boxer dog!
14. Well-demarcated, circular, erythematous, alopecic nodules located on the face or distal extremities of a dog which when examined closely reveal minute fistulous tracks.
15. Well-demarcated alopecic area of erosion or ulceration with or without palpable nodules located near the axilla on the lateral body wall of a middle-aged or older dog. Lesions are not pruritic but elicit grooming.
16. Coalescing nodules with draining fistulous tracts located on the muzzle of a cat.
17. Generalized alopecia with exfoliation with areas of increased severity affecting the head and neck in a cat. Facial skin commonly is thickened with narrowing of the eyelid margins.
18. Painful, focal or multifocal, eroded coalescing alopecic plaques located ventral to the ear, or elsewhere on the face of a golden retriever.
19. Syrup-like viscid fluid emanating from a traumatized bleb or skin biopsy hole in a dog.
20. Depressed puppy less than 4 months of age initially presented with a remarkably exudative otitis externa.
21. Symmetric non-draining deformed enlargement of the planum nasale in a dog.
22. Asymptomatic, multicentric ulcerated, cavitated, crateriform masses in the skin of a dog.
23. Firm, well-demarcated, sometimes gritty alopecic plaques with a whitish 'feathery' look to the margin of the lesion.
24. Coalescing nodular dermal lesions with patchy alopecia and broken hairs in a Persian cat.
25. Partial or complete alopecia markedly restricted to areas with certain hair color.
Please do not view the answers until you have viewed the presentation!
Clinical Markers of Selected Dermatoses: Visual Clues--Answers
1. Feline paraneoplastic alopecia
2. Linear preputial erythema--Sertoli cell tumor
3. Facial dermatitis of Persian and Himalayan cats
4. Pemphigus vulgaris (autoimmune skin diseases affecting intercellular bridges)
5. Bullous pemphigoid (autoimmune skin diseases affecting the basement membrane zone)
6. Demodicosis comedones
7. Post rabies vaccination alopecia
8. Feline skin fragility syndrome
9. Facial depigmentation (DLE, VKH, vitiligo, MF)
10. 'Do not violate planum'--follicular diseases (dermatophytosis, demodicosis, pyoderma)
11. Topical application corticosteroid reaction
12. Adverse drug reaction (with umbilicated lesions)
13. Canine leproid granuloma
14. Kerion dermatophytosis
15. Sweat gland adenocarcinoma
17. Degenerative mucinotic mural folliculitis
18. Pyotraumatic furunculosis
20. Juvenile cellulitis (juvenile sterile granulomatous dermatitis & lymphadenitis)
21. Histiocytosis of the planum nasale (clown nose disease!)
22. Subgroup of cutaneous lymphosarcoma
23. Calcinosis cutis
24. Dermatophytic pseudomycetoma
25. Black-hair follicle dysplasia (color dilution alopecia)