Primary Care Dermatology

Kara Mudd, MSPAS, PA-C

The Skin

• Accounts for ~15% of the total body weight and is the largest organ in the

human body.

• The Skin serves many functions

• Physical barrier to chemical or mechanical insults, microbes, regulates hydration

• Sensory- mechanoreceptors

• Metabolic- Vit D3 synthesis

• Immunologic protection

• Thermoregulation

Anatomy of the skin

Anatomy of the skin

• The skin is made up of three main layers

• Epidermis

• Dermis

• Subcutis/Subcutaneous layer

Anatomy of the skin

• Epidermis – made up mainly of keratinocytes (90%)

• Layers of the Epidermis- (Come Lets Get Sun burned)

• Stratum Corneum- Made up of desquamating keratinocytes.

• Stratum Lucidum (present in palms and soles)

• Stratum Granulosum- Keratinocytes secrete lipids into the extracellular space in this

layer to give the skin its water protective barrier as well as helping the skin to retain moisture

• Stratum Spinosum- desmosomes between keratinocytes hold the cells together and give this layer a “spiny” look under the microscope

• Stratum Basale- Epidermal stem cells divide here to start keratinization

Anatomy of the skin

Anatomy of the skin

• Epidermis – made up mainly of keratinocytes.

• Keratinocytes- This is the predominant cell type in the epidermis. In the basal

layer keratinocytes are referred to as basal cells. They undergo multiplication

and migrate up through the layers of the epidermis. They accumulate keratin

as they move upward through the layers and are shed through desquamation.

This cycle takes approximately 30 days.

Anatomy of the skin - Epidermis

• Melanocytes- Found among the basal layer and in hair follicles. Produce

melanin in melanosomes that protect the nucleus of neighboring

keratinocytes.

• Langerhans Cells – Antigen- presenting cells, most often in the spinous

layer. Bind and present antigens to T lymphocytes. Important in delayed-

type hypersensitivity.

• Merkel Cells- mechanoreceptors for light touch. Increased numbers in

sensitive skin.

Anatomy of the skin

• Dermal-Epidermal Junction

• Separated by the basement membrane.

• Dermal papillae and epidermal rete ridges help facilitate the stability of the

junction

• If this junction is affected it can cause blistering

Anatomy of the skin

Anatomy of the skin

• Dermis – Layer of connective tissue that supports the epidermis and binds it

to the subcutaneous tissue. Network of blood and lymphatic vessels.

Dermal vasculature has a thermoregulatory function. Also contains hair

follicles and sweat glands.

• Papillary Layer- thin contains the dermal papillae, collagen

• Reticular Layer- more dense type I collagen, elastic fibers

• Varying thickness based on area of the body. Maximum thickness 4mm.

Anatomy of the skin

• Adnexal Structures-

• Sebaceous Glands- secrete sebum, in dermis

• Hair follicle- epidermal invagination, keratin form hair shaft

• Sweat Gland

• Eccrine- widely distributed, direct opening onto skin, main role in thermoregulation

• Apocrine- connected to the hair follicle (axillae, areola, perianal, genital)

Anatomy of the skin - Pilosebaceous unit

Anatomy of the Skin- nails

• Cuticle- stratum corneum

• Nail Matrix produces nail

• Nail Plate- bound to epidermis

• Nail Bed- contains stratum basale and stratum spinousum

• Fingernails grown ~3mm/mo

• Toenails grow ~ 1mm/mo

Evaluation of the Dermatology Patient

Distribution of dermatologic diseases

Dermatology Terminology- Primary Lesions

Macule- Flat, nonpalpable, typically well circumscribed lesion <10 mm in

diameter

Dermatology Terminology- primary lesions

Papule- firm, palpable, well circumscribed <10mm diameter

Dermatology Terminology- primary lesions

Patch- flat, non palpable, >10mm diameter,

Dermatology Terminology

Nodule- raised, palpable lesion, well circumscribed >10 mm in diameter,

deeper in dermis

Dermatology Terminology

Plaque- raised flat top lesion, > 10mm, may be a group of confluent papules

Dermatology Terminology

Vesicle- elevated, well

circumscribed, containing serous

fluid, < 10mm

Bulla- well circumscribed, raised, fluid

filled, >10mm

Dermatology Terminology

Wheal- elevated, irregular shaped area of edema, transient

Dermatology Terminology

Pustule- elevated, superficial, filled with purulent fluid

Dermatology Terminology

Telangiectasia- fine capillary dilation

Dermatology Terminology

Cyst- elevated, encapsulated lesion filled with liquid or semi-solid

Dermatology Terminology

Petechiae/Purpura- extravasation of red blood cells, non blanching

Dermatology Terminology

Atrophy-thinning of skin, skin becomes paper like

Dermatology Terminology

Erosion- Loss of part of the epidermis, follows rupture of vesicle/bulla

Dermatology Terminology

Excoriation- loss of the epidermis, often with eschar

Ex: scratch, scabies

Dermatology Terminology

Fissure- linear break all the way to the dermis

Dermatology Terminology

Lichenification- thickened epidermis, well circumscribed

Dermatology Terminology

Scale- desquamation, keratinized cells

Dermatology Terminology

Scar- fibrous tissue that replaces normal skin following an injury

Dermatology Terminology

Ulcer- loss of epidermis and dermis

Dermatology Terminology

Crust- hardened serum, blood or purulent exudates

Dermatology Terminology

Verrucous- rough surface

Diagnostic Tests

• Diascopy- Using a diascope or glass slide pressed up to the skin to

evaluate for intact capillaries vs. extravasated blood.

Diagnostic Tests

• Mineral Oil scraping for mites-

Diagnostic Tests

• KOH prep- If it’s scaly scrape it

Diagnostic Tests

• Tzanck Smear-

• De-roof vesicle and put fluid

on slide, stain with methylene

blue.

• Mutinucleated giant cells are

diagnostic for herpes

infection.

• Viral culture is more practical

and used clinically.

Diagnostic Tests

• Woods Light examination-

• Loss of pigment in Vitiligo.

Depigmented skin fluoresces.

• Tinea Versicolor- yellow

• Erythrasma- corynebacteria

fluoresces coral/pink

• Pseudomonas- green

Diagnostic Tests

• Patch Testing-

Diagnostic Tests

• Biopsy

• Shave biopsy-

• Used for superficial lesions. Skin Cancers, SK’s,

nevi.

• Only removes a thin layer of tissue

• Do not use for inflammatory conditions

• Wound care: wash daily with soap and water.

Apply Vaseline and a bandage daily.

• Do NOT use for suspected Melanoma

Diagnostic Tests

• Biopsy

• Punch biopsy

• Used when the dermis or subcutaneous tissue

needs to be sampled, also could be used for

definitive removal.

• 2-10mm punch biopsies are available. 4mm is

standard.

• Needs to be closed with suture which are

removed in 7 days on face and 10 days on the

trunk or extremities.

• Wound care: wash daily with soap and water.

Apply Vaseline and a bandage daily.

Diagnostic Tests

• Biopsy

• Incisional biopsy- Deep incision to remove a larger

piece of tissue down to the subcutaneous tissue but

not the entire lesion. Often used in a widespread rash

or to take a sample of a large lesion. Closed with

subcutaneous and superficial sutures.

• Excisional biopsy- Excision to attempt to remove the

entire lesion. Could be performed in the case of a

suspected malignancy (malignant melanoma). If

margins not clear would have to go back for wider

excision.

Diagnostic Tests

• Cultures

• Viral Culture- VZV, HSVI/II

• Bacterial Culture- aerobic/anaerobic

• Fungal Culture- onychomycosis, tinea corporis etc.

Questions?

References

• Berger TG. Dermatologic Disorders. In: Papadakis MA, McPhee SJ, Rabow MW.eds. Current Medical Diagnosis & Treatment 2015. New York, NY: McGraw-Hill; 2014.

• Farmer P, Rhatigan J. Global Issues in Medicine. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e. New York, NY: McGraw-Hill; 2015.

• Garg A, Levin NA, Bernhard JD. In: Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ, Wolff K. eds. Fitzpatrick's Dermatology in General Medicine, 8e. New York, NY: McGraw-Hill; 2012.

• Khan SA, Bank J, Song DH, Choi EA. The Skin and Subcutaneous Tissue. In:Brunicardi F, Andersen DK, BilliarTR, Dunn DL, Hunter JG, Matthews JB, Pollock RE. eds. Schwartz's Principles of Surgery, 10e. New York, NY: McGraw-Hill; 2014. LeBlond RF, Brown DD, Suneja M, Szot JF. The Skin and Nails. In: LeBlond RF, Brown DD, Suneja M, Szot JF. eds. DeGowin’s Diagnostic Examination, 10e. New York, NY: McGraw-Hill; 2015.

• Mescher AL. Chapter 18. Skin. In: Mescher AL. eds. Junqueira's Basic Histology: Text & Atlas, 13e. New York, NY: McGraw-Hill; 2013.

References

• Usatine RP, Smith MA, Chumley HS, Mayeaux EJ, Jr.. In: Usatine RP, Smith MA,

Chumley HS, Mayeaux EJ, Jr.. eds. The Color Atlas of Family Medicine, 2e. New

York, NY: McGraw-Hill; 2013.

• Wolff K, Johnson R, Saavedra AP. In: Wolff K, Johnson R, Saavedra

AP. eds. Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology, 7e. New

York, NY: McGraw-Hill; 2013.