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