Foundations of Dermatology, Terminology, & Diagnostics

What are the 3 layers of the skin?

Epidermis, Dermis, Hypodermis

Why does the epidermis have delayed healing?

It is avascular

What form the primary barrier against water loss?

Keratinocytes

What determine pigmentation and UV protection?

Melanocytes

What travels and what stays in stratum basale?

Melanin travels to keratinocytes, melanocytes stay

What does dermis provide?

Strength and elasticity

What does inflammation in the dermis lead to?

Palpable lesions

Vascular supply of dermis explains what?

Erythema and blanching

What does hypodermis act as?

Insulation and energy storage

What does the hypodermis provide?

Cushioning and shock absorption

How fast do infections spread in hypodermis?

Rapidly and become severe

What are the 5 roles of the skin?

Protection, Sensation, Thermoregulation, Protection from UV rays, Synthesis and Storage of Vitamin D

Decreased Vitamin D means what?

Decreased Calcium absorption

What are structures that originate from the epidermis and extend into the dermis?

Appendages

Hair follicles, sebaceous glands, sweat glands

What do sebaceous glands produce?

Oil (Sebum)

What do hair follicles do?

Support hair growth

What do appendages play roles in?

Protection and temperature regulation

What is the Anagen phase of hair growth?

~90% of all follicles are undergoing growth at any 1 time

-2-8 years

What is the Catagen phase of hair growth?

Transitional - lasts several weeks

What is the Telogen phase of hair growth?

Lasts ~3 months, lose ~100 hairs daily

What is the nail matrix?

Nail plate production

What factors influence nail growth?

Age, Systemic Disease, Medications

Inflammation causes what?

Redness, warmth, swelling, and pain

What does immune dysregulation lead to?

Chronic inflammatory disease

What does infection produce?

Localized and systemic signs

What is a primary lesion?

Appear directly as a result of a disease process

What is a secondary lesion?

Develop from primary lesions or due to external forces like scratching, infection, or natural infection

What is a macule?

Flat, non-palpable change in skin color; small ≤ 1 cm

What is a patch?

Large flat macule > 1 cm

What is a papule?

Solid, Elevated/palpable lesion, may be confluent ≤ 1 cm

What is a plaque?

Broad and flat topped. Usually > 1 cm in diameter. Circumscribed palpable solid lesion, plateau-like

What is a nodule?

Palpable, solid lesion that's deeper into dermis or subcutaneous tissue ≥ 1 cm

What is a tumor?

Large nodule (>2.0 cm)

What is a pustule?

Elevated lesions containing pus, varies in size

What are vesicles?

Circumscribed, elevated lesion containing fluid (<1cm)

What is a bullae?

Fluid filled blister greater than 1 cm. A larger version of a vesicle

What is a wheal?

Firm edematous papule or plaques, Transient

What is a purpura?

Generalized term referring to extravasated blood

What is a petechiae?

Small circumscribed punctate foci of extravasation

What are ecchymoses?

Larger confluent areas of extravasation

What are hematoma?

Massive bleeding into the skin from underlying tissue

What are telangiectasia?

Dilated superficial blood vessels

What is a scale? (secondary)

Flakes or excess dead epidermal cells

What is desquamation? (secondary)

Sheet-like scaling of the skin

What is crust/scab? (secondary)

Collection of dired serum and cellular debris

What is erosion? (secondary)

Focal loss of epidermis

Does not extend below the dermoepidermal junction

Heals without scarring

What is an ulcer? (secondary)

Focal loss of epidermis and dermis

Heals with scarring

What is a fissure? (Secondary)?

Linear crack through the epidermis

May extend into the dermis

What is atrophy? (secondary)

Thinning of skin layers

What is lichenification? (secondary)

Thickened skin area with accentuated skin markings

What is scar? (sceondary)

Fibrous tissue replacing normal skin after injury

What is excoriation? (secondary)

Linear or hollowed-out crusted area, caused by scratching

What is discoid?

Round with uniform appearance throughout lesion

What is oval?

Oval with uniform appearance throughout the lesion

What is annular?

Ring shaped with variation in appearance between center and periphery

What is arcuate?

Arc shaped, may be a portion of an annular lesion

What is targetoid?

Target-like with distinct zones

What is grouped?

Clustered next to one another

What is discrete/isolated?

What is discrete/isolated?

Separated from one another

What is linear/streak?

Thin straight line of lesions

What is dermatomal?

Distributed along a dermatome

What is serpinginous?

Wave or snake-like

What is symmetrical generalized/disseminated?

Uniform distribution on both sides of the body

Spread over wide areas of the body

What is photodistributed?

Located in areas of sunlight exposure

What is part of a lesion-focused history?

Onset and evolution of the lesions

Site of onset and pattern of spread

Duration and recurrence

What is a symptom profile?

Itching, pain, burning

Severity and timing

Relieving or worsening factors

What is the exposure history to ask?

- New medications (Rx, OTCs, supplements)

- Travel / sick contacts

- Plants/animals/insects

- Work/hobbies (chemicals, gloves, wet work, athletics)

- Sexual history (when appropriate)

What are systemic contexts?

Fever, malaise, arthralgias

PMHx (autoimmune, immunosuppresion)

Allergies and photosensitivity

When you see a systemic symptom in a context of a rash, what is it?

Emergency

What is part of the Focused History: Tumor or Concerning Lesion?

What changes have occurred in size, shape, color, or appearance?

Does the lesion bleed easily or spontaneously?

Is there a history of significant sun exposure, sunburns, or tanning bed use?

What is the rash description?

1. Distribution (arrangement)

2. Configuration (shapes

? Size (cm) +/-/ Color

3. Morphology (what type of lesions/primary or secondary)

4. Location

What is blanching?

Temporary whitening of the skin when pressure is applied, caused by displacement of blood from superficial capillaries

If the blanching turns white, what is the redness due to?

Blood within intact vessels

If the blanching DOES not turn white, what is the redness due to?

Blood outside vessels or pigment (eg. urticaria, cellulitis)

What is Darier's Sign?

Rubbing a lesion causes local swelling, redness and itching

Why does Darier's Sign happen?

Mast cells in the lesion degranulate, releasing histamine (itching)

What is Nikolsky's sign?

Gentle lateral pressure on the skin causes the epidermis to slough off

What is Auspitz sign?

Pinpoint bleeding when psoriatic scale is scraped off

Classic for psoriasis

How does Auspitz sign happen?

Psoriasis causes thin epidermis over dilated capillaries, scraping exposes these vessels -> pinpoint bleed

What is Koebner's Phenomenon?

Appearance of new skin lesions of a pre-existing dermatitis at sites of trauma or injury

How does Koebner's Phenomenon happen?

Trauma triggers local inflammation and immune activiation, in susceptible skin, this leads to activation of the disease process that's already present elsewhere

What is Shagreen patch?

Thickened, rough skin with a leathery or "orange-peel" texture

Commonly found on the lower back

Excess connective tissue in the skin

Associated with tuberous sclerosis

What is the gold standard when you're uncertain?

Biopsy

When is biopsy used when?

Diagnosis is uncertain

Lesion is atypical

Malignancy is a concern

If it is inflamed, what are signs?

Red, itchy, swollen

Often blanches

Examples: Dermatitis, urticaria

If it is infection, what are signs?

Painful, warm

May have discharge, crusting, fever

Examples: cellulitis, impetigo

If it is immune dysregulation, what are signs?

Chronic or relapsing

Symmetric or widespread

Examples: Psoriasis, lupus, atopic dermatitis

When is KOH prep used?

Suspected fungal infection

When should you use Culture?

Purulent or worsening lesions

When should you use Wood's Lamp?

Pigment of infection evaluation

When should you do biopsy?

Unclear or concerning lesions

What does patch testing do?

- Evaluates delayed hypersensitivity reactions

- Identifies causes of allergic contact dermatitis

- Reactions occur hours to days after exposure

What does photopatch testing do?

Identifies UV-dependent reactions

What drives diagnosis?

Morphology + distribution

What is reticular?

Lace or net-like