This document provides an overview of the approach to dermatologic diagnosis. It discusses taking a thorough patient history including symptoms, onset, duration, treatments, and family history. A full physical examination of the skin is important, examining lesions under good light. Primary skin lesions like macules, papules, plaques, nodules, and tumors are described. Secondary lesions including scales, crusts, erosions, ulcers, and scars are also outlined. Special examination techniques like magnification, diascopy, Wood's lamp, and skin biopsies are mentioned which can aid in diagnosis.

1. APPROACH TO DERMATOLOGIC
DIAGNOSIS
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2. History
- itching, burning, rash, generalized/localized eruption,
pain, pigmentary changes, swelling, ulceration etc are
presenting symptoms.
- elaborating enquiries are made about complaints
in terms of onset, duration, progression, distribution,
treatments taken etc
- Hx of similar illness previously or in the family, self &/or
family Hx of atopic Dss & other illness should be
enquired
- occupational & social Hx
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3. • Physical Examination
- At present gross morphology in the form of skin lesions
remains the hard core of dermatological Dx.
- skin lesions are visible to the naked eye
- using the same general principle of clinical Dx makes
the Dx of skin ds.
- A proper skin examination should be performed in good
light preferably in daylight. Ideally the whole skin should
be examined.
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4. Primary skin lesions
• Macule are variously sized,
circumscribed changes in skin
color, without elevation or
depression
• A flat normal surface size <1cm
in diameter
• Eg; Café au lait spot ,Vitiligo
Freckle, Junctional nevi, Tinea
versicolor, Melasma
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5. Papules
• An elevated solid lesion up
to 0.5 cm in diameter; color
varies; papules may become
confluent and form plaques
• Eg: Acrochordan (skin tag),
Acne, Nevus Melanoma,
Molluscum contagiosum
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6. Patches
• Patch…similar to a macule but
size >1cm flammeus or vitiligo.
• Eg: Vitiligo, Nevus flammeus
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7. Plaques
• Is a broad papule (or
confluence of papules), 1
cm or more in diameter and
its diameter is much >
thickness
• Eg: Psoriasis, Eczema, Tinea
corporis, Mycosis fungoides
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8. Nodules
• Solid elevation, >0.5 cm in
diameter, larger deeper
papule and its
thickness=diameter
• Eg: Rheumatoid nodule,
Xanthoma, Lipoma,
Metastatic carcinoma,
Erythema nodosum
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9. Tumors
• Tumors are soft or firm
and freely movable or
fixed masses of various
sizes and shapes (but in
general greater than 2
cm in diameter).
• Eg:Lipomas,
Melanoma, TB
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10. Wheals
• Evanescent, pruritic
edematous, plaque (a
hive)
• Eg:Urticaria,
Dermographism, Urticaria
Pigmentosum
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11. Vesicle
• Papule that contains
clear fluid (a blister),
epidermal, may be
unilocular or
multilocular
• Eg: Herpes simplex
Herpes Zoster Contact
Dermatitis Poison Ivy
Dermatitis
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12. Bulla
• Large vesicle, >0.5 cm
in diameter
• Eg:Pemphigus
Vulgaris, Bullous
Pemphigoid, Bullous
impetigo
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13. Cyst
• Nodule that contains fluid
• Eg: Acne, Epidermal inclusion cyst, Pilar cyst
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14. Secondary Lesions
• Scales (Exfoliation): Thick stratum corneum resulting
from hyper-proliferation or increased cohesion of the
keratinocytes
• Eg: Psoriasis, Toxic Epidermal Necrolysis
,Staphylococcal Scalded Skin Syndrome, Eczema,
Ichthyosis
• Scale…dry/flaky surface due to abnormal stratum
corneum with accumulation of or increased shedding of
keratinocytes
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15. Crusts (Scabs)
• Collection of dry
debris, dried sebum,
pus or blood
• Eg: Impetigo ,Late
syphilis ,Third degree
burns
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16. Excoriations & Abrasions
(Scratch Marks)
• Linear erosions caused by
mechanical means meant it is a
localized damage to the skin due
to scratching
• Eg: Eczema ,Scabies
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17. Fissures (Cracks, Clefts)
• Linear cleft into the epidermis or dermis
• Eg: Dry skin from soaps or detergents,
chapping
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18. Erosions
• Loss of all of the epidermis
(heals without a scar)
• Eg:Herpes zoster, Herpes
simplex, Impetigo, aphtus
ulcer
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19. Ulcers
• Loss of the epidermis and portions of the
dermis (heals with scarring)
• Eg: Basal Cell Carcinoma, Decubitus, vascular
ulcere, Pyoderma gangrinosum
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20. Scars
• New connective tissue replacing the lost
dermal tissue (dermo-epidermal damage)
• Eg: Discoid lupus Hypertrophic scars Keloids
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21. LICHENIFICATION
• Hyperplasia of the epidermis
Meaning thickening of the
epidermis with increased
skin markings due to
persistent scratching.
• Caused by chronic scratching
or rubbing Atopic Dermatitis
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22. ATROPHY
• Thinning of the epidermis and/or dermis
• Eg: Results from topical steroid use or
corticosteroid injections
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23. Descriptions of Skin Lesions
• Number of lesions
• Discrete/ confluent
• Circumscribed (limited or confined)
• Shape: Annular , arcuate , circinate , discoid, guttate,
gyrate, linear, serpiginous, iris, zosteriform…
• Color: Erythema (red), Violaceous (purple)
• Depth: superficial, deep
• Surface changes: Keratosis ,Necrotic, Umbilicated,
Ulcerated
• Configuration: Grouped (lesions in clusters), Linear,
Arciform, Zosteriform
• Distribution: Generalized , Universal
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24. Special Techniques and Procedures in
Dermatology
1. Magnification
2. Diascopy
3. Wood’s Light Examination
4. Percutaneous Testing
5. Mite Examination
6. KOH Examination
7. Tzank Smear
8. Acetic White Acid Test
9. Skin Biopsy
10. Other
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25. Magnification
• Most magnifying glasses are
double-convex lenses
• Magnification power may vary
from 1.5X to 10X
• If it is enough to show tissue
architectural details on the
surface of the skin it is called
Dermatoscope
(epiluminescence microscopy)
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26. 3. Wood's Lamp
• Ultraviolet light of 360 nm wavelength is
obtained by passing the beam through a Wood's
filter composed of nickel oxide containing glass.
• The examination has to be done in a dark room
• Normal skin doesn’t shine.
• Important in early
or fading lesions.
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27. Wood's Lamp (contd.)
 Aids in diagnosis of many skin diseases
 Tinea capitis caused by Microsporum canis - bright
green.
 Active pityriasis versicolor – yellow.
 Fresh urine in porphyria cutanea tarda - reddish.
 Erythrasma - coral red.
 Vitiligo lesions - more white.
 Ashleaf macule in tuberous sclerosis - more
apparent.
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