Practical Approach to Dermatology

Richard P. Usatine, M.D.Director of Medical Student EducationUTHSCSA Department of Family and

Community Medicine

Goals of lecture:

• Demonstrate a practical approach to the diagnosis of skin conditions using pattern recognition

• review dermatology patterns by:– viewing multiple images – distinguishing between common and

uncommon patterns– observing local and regional morphology

Primary Lesions

• Macule• papule• plaque• nodule

• wheal (hive)• pustule• vesicle• bulla

TINEA VERSICOLOR

DERMATOFIBROMA

Secondary (Sequential) Lesions

• scale• crusts• erosion• ulcer

• fissure• atrophy• excoriation• lichenification

Strategies for Diagnosis

• Use magnification• Feel lightly• Palpate deeply• Distribution• Local patterns - groups, rings, lines

Looking for clues beyond the rash

• Look at nails, hair, mucus membranes, hands, feet– nail pitting for psoriasis– scalp may be clue to seborrhea elsewhere– lichen planus may show a white lacy pattern in

the mouth– fungal infection on the feet with ID reaction on

the hand

Think Pathophysiology

• Infections• Inflammatory Processes - dermatitis,

seborrhea• Acne and related disorders• Immunologic• Benign and premalignant growths• Malignancies

Infections

• bacterial• viral• fungal• infestations

Bacterial infections of skin

• Impetigo, cellulitis, abscess• Folliculitis• Furuncle, carbuncle, abscess• Necrotizing fasciitis• Erythrasma, • pitted keratolysis

Impetigo

• superficial skin infection of the epidermis • characterized by translucent (“honey”)

crusts • caused by S. aureus and strep. pyogenes

(GABHS) • Cephalexin and Dicloxacillin• Bactroban topical

Ecthyma and Bullous Impetigo

• Two variations of impetigo• Ecthyma has a ulcerated “punched-out”

base • Bullous impetigo is more often caused by S.

aureus

Erysipelas

• specific type of superficial cellulitis • prominent lymphatic involvement.• GABHS; H. flu in children• face or leg• admit if toxic or extensive involvement• otherwise, oral Augmentin with close

follow-up

Flesh-Eating Bacteria

• Necrotizing Fasciitis - Type 1 – Mixed anaerobes– Gram negative aerobic bacilli– Enterococci

• Type 2– Group A strep

• Bisno, Stevens. Streptococcal Infections, NEJM, Jan 1996

Diagnosis of Necrotizing Fasciitis

• diffuse swelling of arm or leg• follow by bullae with clear fluid which

become violaceous in color • marked systemic symptoms• can lead to cutaneous gangrene,

myonecrosis, and shock

Cellulitis vs. Necrotizing Fasciitis

• necrotizing fasciitis may look like cellulitis at first

• cellulitis only requires antibiotics• necrotizing fasciitis requires surgical

debridement along with antibiotics

Viral

• HPV• Herpes• Varicella/Zoster

Burrow

Infestations

• scabies - Elimite• lice - Nix• Permethrin

Fungal Infections

• Tinea pedis• Tinea capitis• Tinea corporis• Tinea cruris• Onychomycosis• Tinea versicolor

Granuloma annulare

Common Types of Dermatitis (Inflammation)

• Hand Eczema• Atopic Dermatitis• Contact Dermatitis• Seborrheic Dermatitis

Cutaneous Anthrax MRIMRI

Take home points

• Learn the patterns• Look at nails, hair, mucus membranes,

hands, feet for clues to diagnosis• Use understanding of patterns