Dermatology Flashcards
Give 5 functions of the skin?
Protection
- From water, toxins, mechanical trauma, UV light, microrganisms
- From evaporation
- From infection
- Horns: from predators/sexual competitors
Production of glandular secretions
- sebum, sweat, vit D, pheromones, milk
Sensory
Storage (fat)
Thermoregulation
Communication
- (pheromones, visual, camouflage, aggression/reproduction)
Identify these organisms, found on cytology of the ear of a dog?
Malassezia sp
.What is the most common bacterial pathogen in the dog?
Staphylococcus pseudintermedius
(previously Staphylococcus intermedius)
Where is the periople?
Band of soft rubbery horn over the perioplic dermis of the hoof, proximal to the coronary dermis (rubbery bit over top of coronary band)
To which group of drugs does prednisolone belong?
Glucocorticoids / corticosteroids
Name a single drug that is licensed for the treatment of both fleas and sarcoptic mange in dogs?
Selamectin and sarolaner
In bold highlight the main causes of skin disease?
Outline a brief clinical approach to derm case?
- Signalment (computer record)
-
History
- General health
- Dermatological
-
History
- Clinical examination
- General
- Dermatological
When you’ve done the above you are in position to make a ddx list
- Differential diagnosis/ tentative diagnosis
- Initial diagnostic tests as indicated, eg
- Coat brushing
- Skin scrapes
- Skin cytology
- Dermatophyte culture
- Trichograms
- Wood’s lamp examination
Diagnosis?
- Yes: in a position to give prognosis and treatment
-
No:
- Further investigations, eg
- Blood tests
- Skin biopsies
- Microbial culture
- Trial therapy, if indicated
- Antimicrobial
- Antiparasitic
- (or empirical treatment if investigations declined?)
Why is age so important when considering signalment for derm cases?
<1yo: diseases associated with immunological immaturity (demodicosis, dermatophytosis, juvenile pyoderma), congenital defects
<3yo: Environmental Atopy, follicular dysplasias, keratinisation defects, histiocytomas (unusual neoplasm as occurs in young animals predominantly)
>6yo: hypothyroidism, hyperadrenocorticism, neoplasia, unlikely to be environmental
When taking a dermatological history what do you need to know?
- Age animal acquired
- Details of in-contact animals – skin problems?
- Lesions on in-contact people?
- How long owned Housing?
- Management?
- Travelled abroad?
- Past dermatological history Onset of current problem – When?
- Nature of lesions?
- Areas of body affected?
- Progression?
- Seasonality?
- Treatments given and response Flea control?
- What and when?
- Exposure to potential sources of infection
Outline a good dermatological exam?
Be thorough and systematic
- Remember ears, interdigital spaces, claws, footpads, mucous membranes
Need
- Good lighting
- Adequate restraint (sedate if necessary)
- Clip hair? (with permission!)
- Identify and record lesions, lesion groupings
Describe this?
Lichenification, erythema, alopoecia, scaling and crusty. Bilaterally symmetrical.
Describe this?
Erythematous, hyperpigmented generalised effected neck ventral region and cranial caudal
Describe this?
Erosions and papules
Outline dermatological practical diagnostic techniques?
When do we use stained vs unstained acetate tape strip?
Unstained acetate tape strip: surface mites etc. ectoparasites
Stained: Looking for bacteria
What are the approximate sizes (µm) of
Malassezia
Staphylococcus bacterium
Cheyletiella mite
Corneocyte
Neutrophil?
With regards parasites which would each of the below investigative techniques be best for?
Coat brushings
Coat combings
Acetate tape unstained
Skin scrapins (superficial and deep)
Plucks
Biopsy
Earwax exam
Coat brushings: Flea dirts – wet paper test
Coat combings: Examine in liquid paraffin under coverslip. Eg. Cheyletiella (mites, eggs)
Acetate tape samples (unstained): Eg Cheyletiella (mites, eggs)
Skin scrapings Liquid paraffin (LP) or KOH/Under coverslip
Superficial: Cheyletiella. Sarcoptes scabiei
Deep: Demodex
Additional techniques for diagnosis of demodicosis: Plucks especially feet, Biopsy
Examination of ear wax in LP:Otodectes
What can a wood’s lamp detect?
Dermatophytosis
Many false negatives (only detects microsporum canis though)
If after you have taken a trichogram the distal tips are broken what is this suggestive of?
Self trauma
What do these two trichograms show?
Dermatophytosis
Hairs covered with spores, penetrated by hyphae (top)
Melanin clumping
colour dilution alopecia (bottom)
How do you differentiate between different stages of hair development?
When should you do skin biopsies?
To establish a definitive diagnosis that cannot be reached by other, less invasive, testing methods. We do it if:
- Suspected neoplasm
- Persistent ulceration/vesicular lesions
- Skin disease unresponsive to rational treatment
- Unusual or apparently serious disease, especially if animal unwell
- Before using dangerous or expensive drugs
What are the basic structures in the skin?
- Epidermis
- Dermis
What are the layers in the epidermis (and in which order are they formed)? How do the cells change as they move towards the surface?
The basal layer
Spinous layer
Granular layer
Horny layer
Cells are called keratinocytes
They are polyhedral cells
They become flatter, anuclear, more keratinised,
How are the epidermal cells joined to each other?
Desmosomes (cell to cell) and hemi-desmosomes (cell to dermal proteins)
There are also tight junctions cell to cell
Define primary and secondary lesions?
Primary lesions are physical changes in the skin considered to be caused directly by the disease process. Types of primary lesions are rarely specific to a single disease entity
Secondary lesions are those which evolve from primary lesions or develop as a consequence of the patient’s activities.
Name some primary lesions?
Name secondary lesions?
Define a papule?
Define a nodule?
What is a macule?
What is a patch?
A circumscribed area of discoloration, greater than 1 cm, which is neither elevated or depressed relative to the surrounding skin
What is a vesicle?
What is a bulla?
A large blister containing serous fluid. A large vesicle is called a bulla – over 1cm.
What is an erosion?
An erosion is a discontinuity of the skin exhibiting incomplete loss of the epidermis, a lesion that is moist, circumscribed, and usually depressed.
What is an ulcer?
An ulcer is a sore on the skin or a mucous membrane, accompanied by the disintegration of tissue.Ulcers can result in complete loss of the epidermis and often portions of the dermis and even subcutaneous fat.
What is scale?
Accumulation of loose fragments of the stratum corneum
What is crusting?
Secondary lesion. Dried exudate, serum, blood, medications or excessive scale on the skin surface; often sequel to a pustule (lay term: “scab”)
What is aconthosis?
diffuse epidermal hyperplasia (thickening of the skin). Acanthosis: increased depth of epidermis – more layers
What is Hyperkeratosis?
Abnormal thickening of the outer layer of the skin. Hyperkeratosis: increased depth of cornified layer – more layers
Names of major myiasis flies?
Warble flies
Bot flies
Sarcophagidae (flesh flies)
Caliphoridae (blow/bottle flies)
Muscadae (house flies)
Names of the common nuisance flies affecting livestock and horses?
Muscidae: house, head, stable and horn flies
How do you distinguish between sucking vs chewing (biting) lice?
Their head
Sucking lice have an almost pointy head
Chewing- very broad
Name lice of different species?
What feature(s) distinguish surface from deep mites?
The length of their legs
Surface: long legs, pointy and backward facing hairs
Burrowing: rounded with short legs, can tuck their legs inside themselves
Name different mites that effect different species?
Identify surface mites from pictures?
Name some burrowing mites from pictures?
How would you distinguish between Ixodes spp, Dermacentor spp and Rhipicephalus spp?
Rhipicephalus- festoons have an ungulated edge. It’s anal groove in a wine shaped Y, which makes it identifiable from dermacentor. It also has no patterns on its back
Ixodes: anal groove is IN FRONT of the anus – more rostral to the anus. Very plain
Illustrate the defining features of Ixodes?
Illustrate the identifying marks of dermacentor?
What are the identifying marks of rhipicephalus?
Which bacterium (genus and species) is the most common cause of canine skin infections? Is it Gram positive or Gram negative?
Staphylococcus pseudointermedius
Gram positive
What are the common sites for staphylococcus and malassezia infection in dog?
Name the four types of hypersensitivity reactions?
Describe Type 1 hypersensitivity reaction?
Type 1:
- Rapid (occurs within 1-3O mins)
- IgE mediated
- Allergens:
- Pollen, mite faeces, flea saliva, food
- e.g Atopic dermatitis, Asthma, Food allergy
Describe type 2 hypersensitivity reactions?
Type 2:
- Occurs within 5-10h
- Antibody recognises self antigen on host cell or tissue
- Autoimmune
- e.g Haemolytic anaemia, myasthenia gravis, pemphigus
Describe type 3 hypersensitivity reactions?
Type 3:
- Reaction maximal at ~4-8h
- Immune mediate complex
- Deposition of small antibody/antigen complexes which escape the normal route of clearance
- e.g Lupus, nephritis, polyarthritis
Describe type 4 hypersensitivity reactions?
Type 4:
- Occurs within 24-72h
- T cell mediated
- Involves dendritic cells and primed T cells
- e.g SICCT
Eosinophilic granuloma complex is described as a cutaneous reaction pattern in cats.
Eosinophilic plaque is one form of eosinophilic granuloma complex.
In what other forms does it occur?
Eosinophilic plaque
Raised, flat-topped erythematous plaques
Usually pruritic
Usually ventral abdomen/caudal thigh
Indolent ulcer (‘Rodent ulcer’)
Erosive/ulcerated lesion on mucocutaneous junction of upper lips
Unilateral/bilateral
Eosinophilic granuloma
Mainly caudal thighs, oral cavity, feet, but can occur anywhere. Occasional ‘fat chin’
Well-demarcated, solid, raised, erythematous plaques/nodules
Eroded or ulcerated surface
+/- exudation, crust
What could this be?
Eosinophilic granuloma
Mainly caudal thighs, oral cavity, feet, but can occur anywhere. Occasional ‘fat chin’
Well-demarcated, solid, raised, erythematous plaques/nodules
Eroded or ulcerated surface
+/- exudation, crust
What could this be on a cat?
Eosinophilic plaque
Raised, flat-topped erythematous plaques
Usually pruritic
Usually ventral abdomen/caudal thigh
What could this be?
Indolent ulcer (‘Rodent ulcer’)
Erosive/ulcerated lesion on mucocutaneous junction of upper lips
Unilateral/bilateral
Rarely painful or pruritic
