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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
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
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
Fungal Infections
• Tinea pedis• Tinea capitis• Tinea corporis• Tinea cruris• Onychomycosis• Tinea versicolor
Common Types of Dermatitis (Inflammation)
• Hand Eczema• Atopic Dermatitis• Contact Dermatitis• Seborrheic Dermatitis