Intro to Dermatology Flashcards
What should you think of in puppies with hair loss?
- Causes of folliculitis
- Food allergies
- Scabies
What should you think of in older dogs with hair loss or infection?
- Need to rule out underlying endocrine causes
When do congenital or hereditary conditions start approximately?
- around 8 weeks
What are the three main causes of folliculitis?***
KNOW THIS
- Bacterial pyoderma
- Demodicosis
- Ringworm
What breeds get allergies?
- Terriers
- Labradors
- Frenchies
What breed gets seborrhea?
- Cocker spaniels
What breed gets hypothyroidism?
- Doberman pinscher
What type of animal gets reproductive hormone endocrinopathies?
- Intact animals
What should you think of with an intact male or a male dog with feminization features?
- Sertoli cell tumor
- If they are castrated, look for a retained testicle
What do Blue Dobermans get?
- Color dilution alopecia
What do lightly pigmented breeds get?
- Solar dermatoses
What can be one of the most important aspects of diagnosing skin disease?
- History
What questions should you ask for a history with skin disease?
- Itching, and how itchy is it?
- When did it start?
- Seasonal or non-seasonal
- Which comes first (itching, alopecia, pustules)?
- Any changes at home/foods?
- Flea medication?
- Is anyone else affected?***
How should you describe dermatologic conditions?
- BE SPECIFIC (Color, size, shape, symmetry, location)
- Describe/think of distribution
- Describe severity (mild, moderate, severe)
Primary dermatologic lesion
- Early lesions that suggest the disease process
Secondary dermatologic lesion
- Usually late in the disease process and secondary to underlying processes or self-trauma
Is a macule a primary or secondary lesion?
- Primary
Describe a macule
- Circumscribed flat spot up to 1 cm
- Non-palpable
What is a macule?
- Melanin (e.g. melanotic macule), depigmentation, erythema, local hemorrhage
Describe a patch
- Macule >1 cm in diameter
- Same possibilities as macules (depigmentation, melanin, erythema, hemorrhage, etc.)
What are differentials for melanotic macules or patches?
- post-inflammatory lentigo
- early melanoma
- Sex hormone dermatoses
What is lentigo simplex?
- Black macules on the gums of orange cats
- These are incidental findings
Differentials for depigmented macules or patches?
- Post-inflammatory
- Immune-mediated (discoid lupus erythematosus)
- Vitiligo
- Drug eruption
Differentials for erythematous macules or patches?
- Acute dermatitis (allergic, parasitic, bacterial, auto-immune/immune-mediated)
- Hemorrhagic (vasculopathy or coagulopathy)
Are papules primary or secondary lesions?**
Primary
Describe a papule**
- Solid elevation up to 1 cm
- Often erythematous
- Palpable
What is a papule?**
- Infiltration of cells (neutrophils or red blood cells)
What type of disease process should you think of when you see a papule?**
- Think INFECTION
Differentials for papules?***
- PYODERMA
- Parasites (Demodex, scabies, etc.)
- Allergy (flea, food, contact)
- feline miliary dermatitis
- Calcinosis cutis
Describe a plaque
- Larger, flat-topped elevation formed by extension or coalition of papules
- Often exudative or glistening
Dfdx for plaques
- Same as for papules and chronic inflammatory disease (pyoderma**, parasites, allergy from flea/food/contact, feline miliary dermatitis, calcinosis cutis)
- Eosinophilic granuloma
Describe a pustule**
- Small circumscribed elevation of skin filled with pus
Differentials for a pustule***
YOU NEED TO KNOW THIS**
- Folliculitis (demodicosis, bacterial pyoderma, dermatophytosis), sterile eosinophilic pustulosis
- Non-follicular (pyoderma, pemphigus foliaceus, sterile eosinophilic pustulosis, drug eruption)
Is a pustule primary or secondary?
- Primary lesion
Because you should know this, what are the follicular differentials for a pustule?
- demodicosis
- bacterial pyoderma
- dermatophytosis
- Sterile eosinophilic pustulosis
Because you should know this, what are the non-follicular differentials for a pustule?
- Pemphigus foliaceus
- Sterile eosinophilic pustulosis
- Drug eruption
- Pyoderma
Describe a vesicle
- Circumscribed lesion; up to 1 cm filled with clear fluid
- Rarely seen because they often rupture
What happens when a vesicle ruptures?
- Turns into a crust
Is a vesicle a primary or a secondary lesion?
- Primary
What types of disease process do clear vesicles most often suggest in small animals and large animals?
- Small animal: auto-immune
- Large animal: viral
What should you think with hemorrhagic vesicles?
- Infectious
Describe a bulla
- Vesicle that is >1 cm
Describe a wheal (i.e. hives)
- Circumscribed raised lesion consisting of edema
Time frame of wheals
- Appears/disappears within minutes or hours
Are wheals primary or secondary lesions?
- Primary
What is something you must differentiate from wheals or hives?
- Pyoderma or folliculitis
How can you differentiate pyoderma/folliculitis from wheals/hives?
- If the hives don’t go away after treatment with anti-inflammatory medications
Differentials for wheals
- Urticaria
- Insect bites
- Positive reaction on intradermal skin test
Urticaria
- basically hives?
Describe a nodule**
- Circumscribed solid elevation >1 cm
- Results from massive infiltration of inflammatory or neoplastic cells into the dermis or subcutis
Differentials for nodules**
- Infectious disease
- Neoplasia
- Sterile causes (that’s then being traumatized)
What is a tumor?
- Neoplastic enlargement of any structure of the skin
Is a nodule a primary or secondary dermatopathy?
- Primary
Is a tumor a primary or secondary dermatopathy?
- Primary
Differentials for tumor
- Infectious
- Sterile
- Neoplasia
What is a cyst?
- A cyst is an epithelial-lined cavity with fluid or solid material
Is a cyst a primary or secondary lesion?
- Primary
What are some examples of things that cysts can be filled with, and what will it look like??
- keratin (toothpaste like)
- Apocrine (fluid)
- Sebaceous
Differentials for a cyst?
- Follicular (inclusion) cyst
- Apocrine sweat gland cyst
- Sebaceous cyst (rare)
Are secondary lesions specific?
- No, they are not specific for the disease causing them
What causes secondary lesions most often?
- Inflammation or self-trauma
Describe epidermal collarettes***
- Circular area of alopecia with loose keratin (scale) around the periphery
Are epidermal collarettes primary or secondary?
- Footprint of pyoderma
What diseases do epidermal collarettes often suggest?
- Pyoderma or infection
- Could be allergy too
What do epidermal collarettes often get confused as?
- Dermatophytosis
How can you help distinguish epidermal collarettes from dermatophytosis?
- Dermatophytosis is often more erythematous and ring-like
- Epidermal collarettes are more ring-like and hyperpigmented
Differentials for epidermal collarettes?**
- Bacterial pyoderma**
- Less often: autoimmune or immune-mediated; dermatophytosis, demodex
- Think about your folliculitis differentials
Describe crusts**
- Dried exudate composed of serum, pus, blood, cells, scales, medications on surface of skin
- It’s not a scab! (slash it is but don’t call it that!)
Are crusts primary or secondary lesions?
- They are secondary lesions
Differentials for hemorrhagic crusts?
- Self trauma
- Pyoderma
- Demodex
- Dermatophytosis
- Parasites
- Auto-immune
Differentials for yellow crusts?
- Pyoderma
- Pemphigus foliaceus
- Distribution can help you
Differentials for crusts on the footpads?
- Pemphigus foliaceus
- Zinc responsive dermatophytosis
- Hepatocutaneous syndrome
- Distemper
Describe a scar?
- Area of fibrous tissue that has replaced the damaged dermis or subcutis
- Alopecic
- Depigmented
- Atrophic
Are scars primary or secondary lesions?
- Secondary
Differentials for a scar?
- Previous severe damage to the skin
Describe an excoriation
- LINEAR superficial removal of epidermis by scratching, biting, rubbing
- Usually self-induced
- Can be erosions or ulcers
Differentials for excoriation
- Self-trauma
What do excoriations suggest about a patient?
- That the patient is itchy
Are excoriations primary or secondary?
Secondary
Describe an erosion
- Break in the continuity of the epidermis
- Does not penetrate basement membrane zone
How does an erosion heal?
- Without scarring
Differentials for erosions?
- SElf trauma from allergies or ectoparasites
- Auto-immune/immune-mediated
Describe an ulcer?
- Deeper break in the epidermis that penetrates the dermis
Does an ulcer heal with or without scarring?
- Heals with scarring
Are ulcers primary or secondary?
- They are secondary
Ulcer differential diagnoses
- Severe trauma
- Deep pyoderma
- Fungal
- Neoplasia
- Autoimmune/immune-mediated
- Eosinophilic granuloma complex
Describe lichenification
- Thickened, hardened skin with exaggerated superficial skin markings
- “elephant skin”
- Typically hyperpigmented
What does lichenification suggest about the timeline of a disease?
- Chronicity
Differential diagnoses for lichenification
- Chronic trauma (usually secondary to pruritus), chronic inflammatory/infectious changes
What are animals with lichenification often secondarily infected with?
- Pyoderma (surface)
- Yeast
Is lichenification primary or secondary?
- Often secondary
Describe hyperkeratosis
- Increase in the thickness of the cornified layer of the skin
Differentials for hyperkeratosis if it’s on the nose, elbows, feet pads?
- Old age change, callus
Differentials for hyperkeratosis if it’s on the feet pads?
- Pemphigus foliaceus
- Zinc responsive dermatosis
- Hepatocutaneous syndrome
- Distemper
Describe a fissure?
- Linear damage into epidermis that may extend into the dermis
- Can be single or multiple
Where do fissures tend to occur?
- Ear margins
- Ocular, nasal, oral, anal mucocutaneous borders
Differentials for fissures
- trauma or disease
- Distemper
- Auto-immune
- Immune-mediated (vasculitis)
Describe a callus
- Thickened, hyperkeratotic, lichenified plaque over bony prominences from chronic friction
Where do calluses form?
- Elbows, hocks, hips, and sternum
- Bony prominences
Are calluses primary or secondary?
- Secondary
Are fissures primary or secondary?
- Secondary
Is alopecia primary or secondary?
- Can be either
Describe alopecia
- Baldness, absence of hair from skin where it is normally present
- Can be patchy (moth eaten)
- Complete
With what diseases can alopecia be primary?
- Endocrinopathies
With what diseases can alopecia be secondary?
- Pyoderma*
- Demodex*
- Dermatophytosis
Differentials for multifocal alopecia?
- Pyoderma*
- Demodex*
- Dermatophytosis*
- Sebaceous adenitis
- Self-trauma
Differentials for symmetrical alopecia?
- Endocrinopathies**
- Telogen defluxion
- Anagen defluxion
- Follicular dysplasias
- Alopecia X
- Self trauma
Describe a scale
- Accumulation of loose fragments of cornified layer of skin
- Consistency and color may vary (oily, waxy, dry; yellow, white, brown)
Is a scale primary or secondary?
- Can be either
Differentials for scales
- Investigate skin closely for pyoderma; otherwise consider causes of seborrhea
Causes of seborrhea
- Ichthyosis
- Primary idiopathic seborrhea
Describe follicular casts
- Accumulation of keratin and follicular material that adheres to the hair shaft
Differentials for follicular casts
- Causes of folliculitis (dermatophytes, bacterial pyoderma, demodex)
- Sebaceous adenitis
- Vitamin A responsive dermatosis, primary seborrhea
Are follicular casts primary or secondary?
- Either
Describe hyperpigmentation
- Increased epidermal and sometimes dermal melanin
Differentials for hyperpigmentation
- Post-inflammatory trauma
- Endocrine disease
- Lentigo
- End result of an epidermal collarette
Is hyperpigmentation primary or secondary?
- Can be either
Describe hypopigmentation
- Loss of epidermal melanin
Differentials for hypopigmentation
- Post-inflammatory
- Immune-mediated
- Vitiligo
- Leukoderma
- Discoid lupus erythematosus
Is hypopigmentation primary or secondary?
- Either
Describe comedomes?
- Dilated hair follicle filled with keratin and sebaceous debris
Differentials for comedomes (and which should be #1)?
- Demodex***
- Endocrine
- Feline acne
- Seborrhea
What should you think if you see lesions on the ventrum?
- Pyoderma
What should you think if you see lesions on the head?
- Demodicosis
What should you think if you see lesions on the ear tips?
- Scabies
- Vasculitis
What should you think if the lesions are on the face/muzzle/head/hears?
- Pemphigus foliaceus
What should you think if the lesions on the flanks and tail tip?
- Endocrine
What should you think for itching/licking paws/overgrooming?
- Allergies/infections until proven otherwise
What should you do diagnostically for a pustule?
- Think folliculitis (bacterial, pyoderma, demodex, dermatophytosis)
- Multiple skin scrapings
- Cytology
- +/- fungal culture
How should you determine a therapeutic plan?
- Interpret your diagnostic test results (e.g. negative skin scrapings or cytology showing PMNs with intracellular bacterial cocci)
- Always think of the patient (severity and distribution of lesions)
- Address the client’s primary complaint
What are the most common client complaints?
- Itching
- Skin/ear infections
