This document provides an overview of dermatological history taking, physical examination, diagnostic testing, and differential diagnosis of skin diseases in dogs. It discusses taking a patient history, performing a physical exam to identify primary and secondary skin lesions, and collecting samples via skin scrapings, trichograms, tape stripping, fungal culture and cytology. A range of parasitic, bacterial, viral, fungal and other infectious and non-infectious dermatological conditions are described. Diagnostic tests include Wood's lamp exam, skin biopsies and bacterial culture. Treatment may involve topical therapies, systemic drugs or surgery.

1. Dermatological History and Examination
Natapol Pumipuntu,DVM

2. Contents
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- History taking
- Physical Examination
- Differential Diagnosis
- Diagnosis Test & Clinical pathology
- Tentative Diagnosis & Definitive Diagnosis
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3. • Parasitic diseases
• Bacterial skin diseases
• Viral, Protozoal and Rickettsial skin disease
• Fungal skin diseases
• Hypersensitivities
• Autoimmune dermatoses

4. • Endocrine dermatoses
• Nutritional dermatoses
• Neoplastic dermatoses
• Psychogenic dermatoses
• Congenital and hereditary dermatoses
• Miscellaneous dermatoses

5. Parasitic diseases
• Demodex canis
• Sarcoptes scabiei
• Otodectes cynotis
• Cheyletiella spp.
• Tick
• Flea
• Fly

6. Demodex canis

7. Sarcoptic mange

8. Otodectes cynotis

9. Bacterial skin diseases
• Staphylococcus intermedius
coagulase-positive & Gram-positive coccus

10. Bacterial skin diseases cont
• Surface infections
- pyotraumatimatic dermatitis
Hotspot
- fold pyoderma

11. Bacterial skin diseases cont
• Superficial infections
- impetigo
- Superficial folliculitis

12. Bacterial skin diseases cont
• Deep infections
- Deep folliculitis
- Deep pyoderma
- cellulitis
- mycobacterial infections

13. Viral, protozoal and
Ricketsettsial skin diseases
• Viral
: canine distemper virus
canine viral papillomatosis etc.
• Protozoal
: canine leishmaniasis etc.
• Bacteria
: Ehrlichia canis etc.

14. Fungal skin diseases
• Fungi
- Microsporum canis
- Microsporum gypseam
- Trichophyton mentagrophytes
• Yeast
- Malassezia patchydermatis

15. Hypersensitivites
• Allergic contact dermatitis
• Inhalant allergy
• Adverse reaction to food
• Drug eruption
etc.

16. Autoimmune dermatoses
• Lupus erythematosus
• Pemphigus foliaceus
• Pemphigoid syndrome
• Alopecia areata
• Discoid lupus erythematosus
• Pemphigus vulgaris

17. Endocrine dermatoses
• Hypothyroidisim
• Hyperadrenocorticism
• Gonadal hormones
• Growth hormone
etc.

18. Nutritional dermatoses
• Protein/calorie deficiency
• Essential fatty acid deficiency
• Vitamin A deficiency
• Vitamin E deficiency
• Zinc deficiency

19. Neoplastic dermatoses
• Tumors of epithelial origin
: Papilloma, Basal cell tumor,
Sebaceous gland tumor,
Squamous cell carcinoma etc.

20. Neoplastic dermatoses cont
• Tumors of mesenchymal origin
: Fibroma, Fibrosarcoma, Lipoma,
Liposacoma, Mast cell tumor etc.

21. Neoplastic dermatoses cont
• Tumors of lymphohistiocytic origin
: Histiocytosis, cutaneous lymphoma,
Transmissible venereal tumor etc.

22. Psychogenic dermatoses
• Lick dermatitis

23. Miscellaneous dermatoses
• Congenital dermatoses
• Hereditary dermatoses
• Keratinization disorder
• Metabolic dermatitis

24. HISTORY
Physical Examination
Treatment
Differential Diagnosis
Diagnosis Test & Clinical Pathology
Tentative Diagnosis or Difinitive Diagnosis

25. History Taking

26. •
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CHIEF COMPLAINT
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28. •
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29. History
• Breed
• Age
• Sex
• Environment
• Diet
• Health status
• History of disease
• Response to previous treatments

30. Physical Examination

31. Physical Examination
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32. Physical Examination
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- Bilaterally symmetric lesion
- Asymmetric lesion

33. Physical Examination
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- Single
- Linear
- Annular

34. LINEAR LESION
ANNULAR LESION
ARCIFORM LESION

35. Physical Examination
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- Primary Lesions
- Secondary Lesions

36. <<Primary Lesions>>
• Macules & Patches
- Discoloration of the skin
- macules  less than 1 cm in diameter
- patches  larger than 1 cm in diameter

37. ***The change is colour may result from pigment
loss or excess, erythema or haemorrhage.

38. Papules & Plaques
• A circumscribed, solid elevation of the skin
• Papules  less than 1 cm in diameter often
pink and red
• Plaques  larger than 1 cm in diameter

40. Pustules
• Circumscribed elevations of the superficial
layers of the epidemis
• Bacterial infection
• The infiltrate will contain neutrophils,
bacteria, debris and perhaps a few free
keratinocytes

41. PUSTULE
**The most important cause is
Staphylococcus intermedius

42. Wheals
• More or less well-defined
elevations of the skin due to edema
• Round, oval or plaque-like
• Disappears within minutes or hours
**angioedema
*Localised mast cell
degranulation within
the skin

43. Vesicles & Bullae
• A well-demarcated elevation of the
superficial layers of the skin
• Vesicles  less than 1 cm in diameter
• Bullae  lager than 1 cm in diameter

45. Nodules
• Circumscribed elevations of the
skin that are larger than the 1 cm in
diameter deeper skin layers

46. Tumors
• Masses of neoplastic origin
whether benign or malignant
• May extend into the deeper
subcutaneous tissue

47. Cysts
• Cavities within the skin that are
lined by epithelium

48. <<Secondary Lesions>>
• Comedones
- dilated hair follicle which contains
a pigmented impaction of lipid
and keratinaceous debris
“BLACK HEAD”

49. Scale
• Associated with the shedding of large rafts
of keratinocytes accumulation of loose
cornified fragment of the epidermis

50. Crust
• Composed of dried exudate mixtd
with debris on the skin surface
serum/blood/pus

51. Exocoriation
• Areas of epidermal damage
caused by scratching, biting or
rubbing

52. Ulceration
• The integrity of the basal layer
basement membrane is
destroyed
• The dermis is involved and healing
is often by scar formation

53. Lichenification
• A thickening of the epidermis with an
accompanying hyperpigmentation in
most instances elephant skin like

54. Hyperpigmentation
• Usually a consequence of melanin
excess
Hypopigmentation
• Loss of pigment

55. Scar
• Occurs when the basal layers of the
epidermis have been breached and
the underlying dermis is damaged

56. &
Problem list ?

57. Problem list?
• Pruritus
• Focal / generalized/symmetrical alopecia
• Crust
• Hyperpigmentation
• Scale
• Nodule
• Patch
• Plaque

58. Diagnostic Test
• Trichogram
Identification of fur mites, adherent egg
cases, fractured ends to the hair shaft
** Trichograms are not a reliable method of diagnosing, or ruling
out, ectoparasite infections

59. Method
• Remove a small tuft of hair with fingers
or forceps
• Laid onto trasparent adhesive tape
• Laid onto a glass slide
• Microscopic examination

60. Adhesive tape stripping
• Allows direct sampling of the coat or skin
surface&hair
• Observes squamous morphology, ectoparasites and
micro-organisms

61. Method
• A commercial, clear, adhesive tape is
gently pressed onto the clipped skin
surface
removed
stained with Diff Quick
Laid across
A glass slide
Laid across a glass slide

62. Skin scraping
• This procedure samples the surface, the
epidermis and the upper dermis
• Indication of Demodex spp., Sarcoptes
scabiei and Cheyletiella spp.
• Indication of dermatophytosis spores

63. Method
• Parasites Clip hair
Liquid paraffin is applied to the skin surface & slide
Dragged across the tensed skin repeatedly by the blade
Transfer accummulated sample to the slide

64. Method
• Dermatophyte
Clip hair
10%KOH applied to the skin surface & slide
Dragged across the tensed skin repeatedly by the blade
Transfer accummulated sample to the slide
Heat fixing
Stained with Lactophenol cotton blue or India ink

65. Wood’s light
• Indication of Microsporum canis,
Microsporum distortum, Microsporum audoinii,
Trichophyton scnoenleinii
• False positive : Pseudomonas spp.,
Corynebacterium spp., keratin, soap,
petroleum and some drugs.

66. Wood lamp examination

67. Fungal culture
• The scale and hair are inoculated onto a
culture plate containing a medium

68. Otic sampling
• Indication of Malassezia
pachydermatis, bacteria and mites
• Method
the sample is collected with a cotton swab
dry
fixing
staining

69. Impression cytology
• Used to sample cells from the surface of
erosions and ulcers or from the orifices of
discharging fistulae
• Medthod
Pressing a cleaned glass slide against the lesion
dry
Staining with Diff Quick

70. Aspiration cytology
• Used to sample cells from within lymph
nodes, nodules and neplasms
• Method Needle aspiration
smear
dry
Staining with Diff Quick or special stain

71. Bacteria Culture
• Indication of aerobic bacteria
Method
the sample is collected with a cotton swab /
aspiration

72. Intradermal skin testing
• Demonstrate the presence of allergen-
specific IgG on the mast cells at the site of
the intradermal injection
• Method

73. Punch biopsy
• Obtain samples for histopathological
examination
• Method Select site
Local anesthesia
Push biopsy punch through the skin
Remove sample & placed into 10% formaline

74. Treatment
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75. • Topical treatment
• Systemic therapy
• Skin surgery

76. THANK YOU FOR YOUR ATTENTION
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