Introduction to Dermatological Diagnosis Flashcards
What is a primary lesion?
Appears quickly and then disappears rapidly
Can then go on to leave behind secondary lesions
What is a secondary skin lesion?
Chronic and evolves from primary skin lesions
How would you describe a macule?
Focal, Circumscribed, non palpable, change in colour, <1cm in diameter
What is the pathogenesis of a macule?
Increased/ Decreased melanin production
erythema due to inflammation or local haemorrhage due to trauma
What is the description of a papule?
Solid, elevated lesion <1cm in diameter
larger lesion is called a plaque
What is the pathogenesis of a papule?
Localised Inflammatory infiltrate
What is the description of a pustule?
Small circumscribed area within the epidermis filled with pus
What is the pathogenesis of a pustule?
Neutrophillic infiltration and infectious in origin
What is the description of a vesicle?
Sharp circumscribed area within or below the epidermis, filled with clear fluid
What is the pathogenesis of a vesicle?
Fluid collection due to inflammation
What is the description of a wheal?
Sharply circumscribed, raised, oedematous lesion, transient
What is the pathogenesis of a wheal?
Subcut oedema
What is the description of a nodule?
Circumscribed, solid raised lesion >1cm in diameter, extends into the deeper layers of the skin
What is the description of an epidermal collarette?
Loose keratin flakes arranged in acircle
What is the pathogenesis of an epidermal collarette?
Remnant of a pustule or vesicle
What is the description of an erosion?
A shallow epidermal defect that does not penetrate the basal membrane- Heals without scarring
What is the pathogenesis of an erosion?
Trauma or inflammation
What is the description of an ulcer?
Break in the continuity of the epidermis with exposure of the underlying dermis, often heals with a scar
What is the pathogenesis of an ulcer?
Severe trauma
What is the pathogenesis of lichenification?
Chronci trauma
What is the description of lichenification?
Thickening and hardening of the skin, Exaggerated superficial skin markings, often hyperpigmented
When would you use a superficial skin scrape?
- Sarcoptes, Notoedres, Cheylitiella, Otodectes
- Scalpel blade used to scrape in the direction of hair growth
- Mineral oil is applied to skin to help collect material
When would you use a deep skin scrape?
- Suspected demodicosis
- Must squeeze the skin to release mites from hair follicles
- Mineral oil applied to the scalpel blade
- Scrape in the direction of the hair until the capillary is bleeding
When would you use an impression smear?
- Ear or skin cytology
- Cotton swab or slide pressed directly onto the lesion
When would you use tape strips?
Useful to identify malassezia
also- cocci, rods, cheyletiella
What is woods lamp used to diagnose?
- Microsporum canis infection
- 50% fluorescence
- Lack of fluorescence doesn’t rule it out so culture is needed
How would you use a fungal culture?
- Sterile toothbrush used to accumulate hairs
- Then applied to the culture medium
- Evaluate daily for 2-3 weeks
How would you do a trichogram?
Pluck hair and evaluate under a low power microscope
also useful for alopecia
What is a fine needle aspiration useful for?
- Useful for solitary lesions
- sample depend son the exfoliating capcity of the lesion
What is a biopsy used for?
- Punch biopsy/ wedhe excision can be used
- site selection is important (take multiple samples)
When would you use allergy testing?
Used in the diagnosis of atopic dermatitis
- must suspect disesae based on the history, clinical signs and examination
What is the difference between serum testing and intradermal testing?
Intradermal testing is considered to be the gold standard
-discontinuation of steroid-containing medications is required
When would you use an elimination diet?
- To confirm or eliminate food allergy dermatitis as a cause of pruritus
- Single protein and carbohydrate source
- Not previously fed
- 6-8 week duration
- then re-challenge
When would you use an insect control trial?
- For insect hypersensitivity
- Environmental and animal flea control
