Dermatology - Dermatophytosis Flashcards Preview

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Flashcards in Dermatology - Dermatophytosis Deck (68)
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1

What is dermatophytosis also known as?

Ringworm - Dr. Noxon said don't call it that

2

What etiologic agents cause dermatophytosis?

Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes, Epidermophyton and other related organisms

3

All etiologic agents of dermatophytosis are zoophilic, except what?

M. gypseum

4

How is dermatophytosis transmitted?

by contact with infected animals, soil, or through fomites

5

What age of animals is more commonly affected by dermatophytosis?

younger animals

6

What are the predisposing factors of dermatophytosis?

poor nutrition, improper sanitation, immunosuppressive diseases, or use of glucocorticoids, and genetic factors

7

What is the pathogenesis of dermatophytosis?

1. Dermatophytes invade and grow in non-viable keratinized tissue
2. Grow only in hairs in anagen, weakening the hair shaft and causing it to break
3. Incubation period of an average of 2 weeks
4. Growing fungus advances down the hair follicle and releases metabolic by-products to incite an inflammatory reaction (folliculitus
5. Type IV hypersensitivity reaction follows
6. Fungus moves to a follicle nearby (outwards) creating a circular lesion

8

What are the classical lesions associated with dermatophytosis?

circular areas of alopecia, patchy alopecia with broken and brittle hair, erythema, hyperkeratinization and crusting, nodular hyperkeratotic erythematous lesions, mild-moderate pruritus may be reported

9

What classical lesions are associated with chronic dermatophytosis?

hyperpigmentation

10

Where are lesions due to dermatophytosis more frequently located?

the head, ears, and extremities

11

What do lesions of dermatophytosis caused by Trichophyton present as?

pustular eruptions

12

What may lesions may onchomycosis cause?

disortion and easily broken claws

13

What are pseudomycetomas?

deep dermal or subcutaneous infections by dermatophytes

14

How do pseudomycetomas present?

as nodules and draining lesions, that histologically are pyogranulomatous to granulomatous panniculitus

15

What is the causitive agent of pseudomycetomas in cats?

M. canis

16

What is the recommended treatment for pseudomycetomas?

surgical excision of the lesion and systemic antifungal therapy

17

What are the methods of diagnosis for dermatophytosis?

Clinical appearance, Wood's light examination, trichogram, fungal culture, and/or skin biopsy

18

What differential diagnoses should be considered when considering dermatophytosis?

scaling disorders such as familial seborrhea, superficial pyoderma, demodicosis, hypothyroidism, and bacterial hypersensitivity

19

True or False: Wood's light examination is a confirmatory test.

False, it is only a screening test

20

What should be examined when doing a Wood's light examination?

the base of the plucked hairs

21

Which fungi that causes dermatophytosis is the only one that flouresces?

M. canis

22

What is a trichogram?

microscopic exam of hair and scrapings

23

Trichograms are an excellent screening test, ___ specificity, _____ sensitivity.

high, moderate

24

What is the most definitive diagnostic test for dermatophytosis?

a fungal culture

25

What samples should be used for a fungal culture?

broken hairs, crusts or scales, and/or individual hairs that fluoresce under the Wood's light

26

Can you use alcohol on areas that you want to take a sample from for a fungal culture?

yes, it can cut down on contaminants

27

What is the MacKenzie Brush technique?

It is a technique that can be used to identify carrier animals - it employs a sterile toothbrush to comb the hair coat of the animal, the bristles are then imbedded or shaken over agar for culture

28

What is the standard fungal culture media?

Sabouraud's dextrose agar

29

What should you be wary of when using dermatophyte test media?

Color change is not diagnostic - you should not base the diagnosis of the organism soley on the color change

30

How do M. canis colonies appear?

as white, fluffy coloniess

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