Practical Approach to
Dermatology
Richard P. Usatine, M.D.
Director of Medical Student Education
UTHSCSA 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
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Macule
papule
plaque
nodule
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wheal (hive)
pustule
vesicle
bulla
TINEA VERSICOLOR
DERMATOFIBROMA
Secondary (Sequential) Lesions
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scale
crusts
erosion
ulcer
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fissure
atrophy
excoriation
lichenification
Strategies for Diagnosis
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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
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bacterial
viral
fungal
infestations
Bacterial infections of skin
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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
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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
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Tinea pedis
Tinea capitis
Tinea corporis
Tinea cruris
Onychomycosis
Tinea versicolor
Granuloma annulare
Common Types of Dermatitis
(Inflammation)
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Hand Eczema
Atopic Dermatitis
Contact Dermatitis
Seborrheic Dermatitis
Cutaneous Anthrax
MRI
MRI
Take home points
• Learn the patterns
• Look at nails, hair, mucus membranes,
hands, feet for clues to diagnosis
• Use understanding of patterns