Intro to Dermatology and Diagnostic methods Flashcards

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1
Q
  1. Pruritus and causes.
  2. With what disorders can scale be seen?
  3. What is alopecia?
  4. What is a bulla?
A
  1. Itching - allergy, parasites, microbial infection/overgrowth, otitis.
  2. Keratinisation disorders.
  3. Hair loss - can be secondary.
  4. Localised collection of fluid >1cm in diameter and larger than a vesicle.
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2
Q
  1. What is erythema?
  2. What is a macule?
A
  1. A diffuse or localised redness of the skin which disappears with diascopy.
  2. A flat circumscribed skin discolouration <1cm in diameter without surface elevation or depression.
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3
Q
  1. 2 main causes of skin being red?
  2. How can these be differentiated?
A
  1. Erythema = blood in blood vessels. Haemorrhage = blood outside of blood vessels.
  2. Diascopy - place glass slide over the area of redness.
    Erythema will blanch as vessels are compressed, haemorrhage will not blanch.
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4
Q
  1. What is a nodule?
  2. What is a papule?
A
  1. Circumscribed solid elevation greater than 1cm usually extending into the dermis, large nodules may be referred to as masses.
  2. A small solid elevation of the skin up to 1cm in diameter, feels solid and is due to the infiltration of inflammatory cells, fluid or foreign material, w/ oedema and epidermal hyperplasia.
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5
Q
  1. What is a patch?
  2. What is a plaque?
  3. What is a pustule?
A
  1. A localised flat change in the skin pigmentation larger than 1cm in diameter (big macule).
  2. Flat topped elevation of the skin >0.5cm formed by a coalition of papules; flatter than a nodule.
  3. A small circumscribed elevation of the epidermis filled w/ purulent material.
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6
Q
  1. What is a vesicle?
  2. What is a wheal?
A
  1. Small circumscribed elevation of the epidermis fille with a clear fluid <1cm in diameter.
  2. A sharply circumscribed raised lesion consisting of oedema; usually appears and disappears w/in minutes to hours.
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7
Q

Causes of secondary lesions.

A

Scratching, chewing, other trauma.
- as a result of infections or may evolve from regressing primary lesions.

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8
Q
  1. What is a comedone?
  2. What is crust?
  3. What is an epidermal collarette?
A
  1. Dilated hair follicle filled w/ cornified cells and sebaceous material. Blackheads.
  2. Dried exudate, cells, pus and scale adherent to the surface.
  3. A circular lesion w/ a marginal rim of scale.
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9
Q
  1. Excoriation/ erosion?
  2. Fissure?
  3. Hyperpigmentation.
  4. Hypopigmentation.
A
  1. Superficial damage to the epidermis.
  2. Linear cleavage into the epidermis.
  3. Too much pigment.
  4. Too little pigment.
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10
Q
  1. Hyperkeratosis?
  2. Lichenification?
A
  1. Increase in thickness of the cornified layer of the skin.
  2. Thickening of the skin as a whole resulting in cobblestone appearance.
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11
Q
  1. What is scale?
  2. Scar?
  3. Ulcer / ulceration?
A
  1. Accumulation of loose fragments of cornified layer of the skin.
  2. Fibrous replacement tissue formed when there has been trauma.
  3. Full thickness loss of epidermis, exposing the dermis.
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12
Q

Diagnostic approach of a dermatological case.

A

General history:
- other body systems affected.
- concurrent disease.
- lifestyle and exposure:
– environment.
– contagion.
- in-contact people and animals.
– contagion and zoonosis.
- diet.
Ectoparasite control.
Identify primary problem.
First sign?
Progression?
- lesion development.
- severity.
Chronic disease.
- seasonal.
- wax and wane.
Response to Tx.
- used appropriately?

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13
Q

Diagnostic techniques in dermatology.

A

Acetate tape:
- Malassezia, bacteria, inflammatory cells.
Skin scraping:
- Deep – demodex mites.
- Superficial – Cheyletiella, Sarcoptes, Chorioptes, Psoroptes (livestock).
Cytology.
Flea comb - fleas, Cheyletiella.
Trichogram (hair pluck) - demodex, anagen, telogen, mite and lice eggs, evidence of pruritus, dermatophytosis (ringworm), hair shaft abnormalities.

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14
Q

Advantages of cytology.

A

Quick, easy, cheap.
Gives a lot of info about what dealing with.

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15
Q

How would a skin scrape be taken from a larger animal e.g. horse w/ itchy distal limb.

A

Wooden tongue depressors to scrape material from skin surface into a petri dish.

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16
Q

Indications for allergen testing.

A

Identify the allergens for potential clinical significance in canine atopic dermatitis or cats w/ feline atopic skin syndrome or horses with allergic skin disease - NOT a diagnostic test.
Provide allergen specific immunotherapy:
- Allergy vaccine / desensitisation / immunotherapy.
- Only use allergen tests w/ high compliant owners who understand limitations of the test and ASIT.
- Need to correlate with history e.g. seasonal or consistent.
Testing younger animals may give a narrower repertoire of allergens than they will have as some hypersensitivities take longer to develop.
Intradermal test.

17
Q
  1. Intradermal test positive control.
  2. Intradermal test negative control.
A
  1. Histamine.
  2. Saline.
18
Q

Allergen specific IgE serology testing in dogs.

A

Heska Allercept test is based on the capture of IgE antibody by the Fc epsilon RI receptor:
- receptor normally binds IgE to a mast cell in vivo.
- binding highly specific for IgE antibody.

ELISA that measures serum IgE using a panel of monoclonal (polyclonal) antibodies specific for dog IgE.
- antigens coated on the ELISA plate.

Tests use a variety of allergen panels including indoor and pollen allergens and fleas.
Only a guide.
“Screening” tests are poorly validated.
Only clinically significant if history relevant.

19
Q

Allergen serology tests that are available.

A

Malassezia - dubious benefit, no proof that positive dogs are hypersensitive or that they will respond well to ASIT.
Staphylococci - again dubious clinical benefit.
Other tests incl. cytology and culture should be used to explore importance of microbial antigens as a cause of pruritus.
Food serology NOT recommended for selecting diets for trialling or diagnosis if “food allergy”.

20
Q

Other dermatological diagnostic testing.

A

Culture:
- bacterial.
- fungal.
- Mycobacteria.
- Susceptibility testing - only helpful for systemic, not topical treatment.
PCR e.g. dermatophyte.
Dermatopathology - biopsy and microscopy.

21
Q

Liver cirrhosis.

A

Chronic ‘end stage’ changed that may arise from a wide range of different causes of liver injury.
- usually repeated injury that has resulted in cell death, chronic inflammation and fibrosis.
– ultimate result = hepatic insufficiency.
- regenerative changes and attempts to increase functional mass but disrupted anatomical and functional aspects of the liver means this mass does not translate to effective hepatic function.

22
Q

What characterises end-stage liver / cirrhosis.

A

Diffuse process that causes fibrosis and conversion of normal liver architecture into structurally abnormal lobules and seriously disturbed hepatic function.
Disturbance of hepatic vasculature - portal-central vascular connections mean increased resistance to blood flow and therefore portal hypertension.
Interspecific and intraspecific differences to liver response but all diffuse.

23
Q

End stage liver / cirrhosis gross features.

A

Grossly abnormal.
Lobes irregular in shape.
Very nodular appearance.
Colour variation.
Changes are diffuse.
Disturbance in normal lobular architecture.
Fibrosis.

24
Q

End stage liver / cirrhosis microscopic changes.

A

Extensive fibrosis - septums and bridging between portal and central areas.
- These can contain vascular channels that can allow blood to by-pass normal hepatocytes and sinusoids.
Fibrosis can surround and disturb interface between hepatocytes and blood so impaired exchange of substances between sinusoidal blood and hepatocytes, interfering w/ normal function.

25
Q

Gall bladder hyperplasia in the dog.

A

Gall bladder mucosa often becomes hyperplastic, and sometime slightly cystic, w/ age - incidental finding in most cases.
Some dogs can get extreme hyperplastic change w/ lots of mucin production = gall bladder mucocele.
- highly thickened gall bladder wall, w/ gelatinous appearance due to mucin production
- can cause signs of biliary obstruction.
- can predispose to thrombosis of gall bladder wall – can lead to gall bladder rupture.

26
Q

Hepatic nodular hyperplasia.

A

Common incidental finding in older dogs.
- occasionally seen in other spp.
1 or a few discrete nodular foci, either w/in hepatic parenchyma or on the surface.
May be up to several cm diameter.
Smooth surface to nodules.
Can be similar colour to surrounding parenchyma or different colour.
Increased hepatocyte number w/in nodules which are well-differentiated and arranged into modified lobules.
No clinical findings.
Need to be differentiated from something that is potentially more severe.

27
Q

What types of primary tumour may arise in the liver?

A

Hepatocellular origin:
- hepatocellular adenoma or carcinoma.
Bile duct epithelium origin:
- cholangiocellular adenoma or carcinoma.
Mesenchymal origin e.g. endothelium, fibroblasts:
- e.g. haemangiosarcoma.

28
Q

Hepatocellular adenoma.

A

Not particularly common.
Usually singular w/in liver - occasionally multiple.
Benign - grow by expansion - spherical.
Well-dermarcated.
Colour varies from similar to rest of liver parenchyma to pale brown/yellow colour.
Unless growth extensive, may not be able to differentiate from nodular hyperplasia.
- probably need histopathological exam to differentiate them from other disease.

29
Q

Hepatocellular carcinoma.

A

Malignant.
Variable appearance.
- sometimes single, massive nodules resembling normal liver.
- sometimes multiple nodules scattered w/in liver – may represent intrahepatic spread of the tumour.
– or multiple tumours are arising simultaneously at different sites.
Can spread to local LNs and sometimes distant sites.

30
Q

Cholangiocellular carcinoma.

A

Can be single or multiple.
Can arise from intrahepatic bile ducts or extrahepatic bile ducts.
Umbilicated appearance - central dip in the tumour.
Can spread intra-hepatically or extrahepatically e.g. local LNs, distant sites.
Tumour mass may start to obstruct the common bile duct, leading to biliary obstruction.

31
Q

Neoplastic metastases to the liver.

A

Lymphoma - can appear nodular or diffuse (mottling or pallor) in the liver
Pancreatic tumours.
Gastric carcinoma.
Mammary tumours.
Haemangiosarcoma e.g. splenic.
Histiocytic.

32
Q
A