This document provides guidance on diagnosing skin diseases. It outlines the key steps which include taking a thorough history, examining the patient for symptoms and signs of skin abnormalities, and performing relevant investigations. The history should explore symptoms of itching, pain, tingling and include questions on duration, triggers, and associated symptoms. The examination classifies primary skin lesions based on features like size, morphology, arrangement and distribution. Secondary lesions resulting from trauma or evolution are also described. Common diagnostic tools like magnifying lenses, glass slides for diascopy, and wood lamps are listed.

1. DIAGNOSIS OF SKIN
DISEASES
Dr. Ayshah Hashimi

2. • Challenge in diagnosing the skin disorder lies in differentiating between normal from abnormal, one lesion
from another and recognising various patterns of distribution
• History taking must include questions related to skin and other systemic symptoms
• Major symptoms of skin disease includes:
 Itching
 Pain
 Paresthesia (tingling sensation)
• Major signs of skin disease includes:
 Rashes and ulcers on skin and mucosa
 Changes on palm and soles
 Changes on hairs and nails
 Discoloration of skin

3. • Following questions should be asked about various skin complaints
1. Itching
• Duration:
 Acute- Scabies, insect bites, dry skin, wound healing
 Chronic- eczema, psoriasis, dermatitis
• Diurnal variation:
 Night- scabies/urticaria
 Day- Photo dermatosis/ Systemic Lupus erythematous
• Precipitating factors:
 Summer- miliaria, teniasis,
 Winters- Psoriasis, Ichthyoses, chilblains
 Sun exposure accelerates photodermatosis
• Associated Symptoms:
 Rash or wheal appears in urticaria, drug rash etc.

4. 2. Pain
• Painful lesion are seen in
 Herpes infection
 Diabetes
 Bedsores
 Ulcers
 Chilblains/ Raynaud’s phenomenon
3. Paresthesia
• Tingling or pricking sensation usually felt in hands and legs due to restricting blood flow to a part of body or
disorders affecting CNS
• Seen in case of tight clothes, fitted shoes or sitting in a washroom for long
• Also observed in raynaud’s disease, hypothermia, carpal tunnel syndrome, sciatica, peripheral neuropathy etc.

5. 4. Rash/ Lesion
• Duration:
 Acute- Scabies, insect bites, urticaria
 Chronic- eczema, psoriasis, dermatitis
• Site of first involvement:
 Centrifugal spread in case of measles
 Centripetal spread is seen in chickenpox, ebola virus
 Acne usually appears on face and back
 Psoriatic lesion affect mainly the extensors and the pressure point while flexors, scalp is involved in
case of seborrheic dermatitis
 Contact dermatitis affects the hand or fingers
 SLE or photo dermatosis affect sun exposed parts

6. • Evolution: how lesion started and then evolved
 Psoriatic lesion turns scaly
 Acne lesion may leave a hyperpigmented scar
 Injury to skin causes hypopigmented scar (Burn/scald)
• Associated symptoms
 Pain in herpes zoster, chilblains,
 Itching in teniasis, dermatitis, psoriasis, urticaria

7. Past History
• History of medication (penicillin, sulfa drugs, anti-seizure drugs, long term use of iron)
• History of medical disorders- diabetes, tuberculosis etc.
Family History
• Hereditary disorders (Ichthyosis, neurofibromatosis)
• Infection and infestation (TB, herpes, scabies)
• Environmental induce- Arsenical keratosis (contaminated water)

8. Examination of primary Lesion
It is described in three terms- morphology, arrangement, distribution
Primary skin lesion are as follows:
Morphology Small (<1cm) Large (>1cm)
Flat with normal texture Macule Patch
Flat and indurated Plaque Plaque
Solid elevated lesion Papule Nodule
Fluid filled lesion Vesicle Bulla
Pus filled lesion Pustule Pustule
Extravasation of blood Petechiae Ecchymosis

9. Macule
• Circumscribed (well defined boundaries)
• Flat lesion
• Size >1cm
• No change in texture of the skin
• Change in colour of the skin
Hyperpigmented
• Brown (melanin is present in epidermis) e.g. freckles, moles, pityriasis
• Violaceous or slate grey (melanin is present in dermis) e.g. lichen planus
FRECKLES
Moles
Pityriasis Lichen planus

10. Hypopigmented/Depigmented
• Less pigmented than surrounding skin e.g. leprosy
• Pigmentation is completely absent e.g. vitiligo
Erythematous
• Pink red lesion either due to
Vascular dilatation (erythema blanches on diascopy)
Extravasation of RBCs (erythema does not blanches on diascopy)
Vitiligo
Leprosy
Vascular dilatation Extravasation of RBCs

11. Papule
• Major portion projects above skin
• Sloid elevated lesion
• Size >1cm
• Can be due to- hyperplasia of cells of epidermis or dermis, metabolic deposits or cellular infiltrates
Surface of papule Disease
1 Smooth Trichoepithelioma (hair follicle tumor)
2 Verrucous (roughened) Verruca vulgaris (HPV infection)
3 Umbilicated (depression in centre) Molluscum contagiosum
4 Scaly Psoriasis
1 2 3 4

12. Shape of papule Disease
1 Dome shaped Milia, neurofibroma
2 Flat topped Plane warts, lichen planus,
3 Filiform Wart
4 Acuminate Condyloma acuminata (genital warts)
5 Sessile Mostly found in skin disorder
6 Pedunculated Skin tags
1 1 3 4
6
5

13. Nodule
• Major component below the skin
• Sloid elevated lesion
• Size <1cm and if size exceeds 2cm it is called as large nodule/tumour
• Have different shape and surface appearances (discussed in previous slide)
• May be epidermal (rare), dermal (dermatofibroma) or subcutaneous (lipoma)

14. Plaque
• Altered texture of skin
• Elevated
• Formed by enlargement or merging of multiple papule
• Have different shapes and contour
Morphology Description Disease
Discoid Uniformly thickened Psoriasis, dermatitis, eczema
Annular Ring shaped Genital Infections (Fungal)
Polycyclic Multiple rings
Arcuate Arc like
Target lesion 3 zones
Centre- dusky erythema
Middle- pallor
Peripheral- erythema
Erythema multiforme

15. Psoriasis
Contact Dermatitis Eczema
Fungal infections

16. Blisters
• Fluid-filled lesion
• Vesicle if < 1cm; bulla 1cm; vesicobullous if both coexist
• Morphologically classified into
 Sub corneal (e.g. Miliaria, impetigo)
 Intraepidermal (e.g. acute eczema, herpes, pemphigus)
 Dermo epidermal (bullous pemphigoid, dermatitis herpetiformis, SLE)
Miliaria Herpes Simplex Pemphigus Dermatitis Herpetiformis

17. Other fluid filled lesions
• Pustule is pus filled vesicle
• Abscess is deep thick walled collection of pus
• Cyst is closed cavity with epithelial lining containing semifluid material
Pustule
Abscess
Sebaceous Cyst
Abscess

18. Lesions due to Extravasation of Blood
• Purpura is erythematous lesion
• No blanching on diascopy
• May be palpable (vasculitis) or nonpalpable (thrombocytopenia)
• If size <1cm Petechiae or >1cm Ecchymosis
• Hematoma is erythematous swelling in specific location E.g. abdomen, brain, nail etc.
Petechiae
Purpura
Ecchymosis
Hematoma

19. Lesions associated with dilatation of blood vessels
• Telangiectasia is visible dilatation of capillaries
• Poikiloderma is triad of atrophy of skin, reticulate hyperpigmentation and telangiectasia
Telangiectasia
Poikiloderma

20. Secondary skin lesion are modifications of primary lesion that occur due to trauma or evolution
Terminology Description Disease
Excoriation loss of epidermis associated with trauma Pityriasis
Lichenification Thickening of the epidermis with exaggeration of normal skin lines,
typically caused by chronic rubbing or scratching of an area
Eczema, lichen
planus
Scales fragments of the stratum corneum as it is shed from the skin Psoriasis
Scar new fibrous tissue which occurs after skin injury Keloid
Ulcer a localized defect in the skin of irregular size and shape where the
epidermis and some dermis have been lost
Fissure a sharply-defined, linear or wedge-shaped tear in the epidermis with
abrupt walls
Dry skin
Striae purple lines on the skin caused by tearing during the rapid growth or
overstretching of skin
Ascites, pregnancy,
obesity

21. Examination of secondary Lesions
Scale
Fragments of the stratum corneum as it is shed from the skin
Varieties of Scale Disease
Silvery Psoriasis
Greasy yellow Seborrheic dermatitis
Branny Pityriasis versicolor
Collarette Pityriasis rosea
Mica like, adherent Pityriasis lichenoid Chronica
Fish like Ichthyosis
Psoriasis
Seborrheic dermatitis
Pityriasis
Ichthyosis

22. Specific Lesions
• Burrow are pathognomonic lesion of scabies
• Comedones are thickened plugs of keratin and sebum
wedged in dilated pilosebaceous orifice. They are
pathognomonic lesion of Acne vulgaris
• Two types-
 Open Comedones are papules with black
keratinous plug
 Closed Comedones are white shiny papules
covered by skin
Scabies
White Comedones
Black Comedones

23. Arrangement and distribution of Lesions
Arrangement Disease
Grouped Herpes Simplex
Scattered Guttate Psoriasis
Linear Psoriasis, Lichen Planus
Dermatomal Herpes Zoster, Leprosy

24. Necessary tools
• Magnifying glass convex lens of short focal length produces 5X magnified picture
• Glass slide is used in Diascopy to differentiate purpura with erythema
• Wood lamp emits UV rays of 365nm wavelength and is used in differentiating epidermal and dermal
pigmentation, fluorescence of different colours are observed e.g. green in tinea capitis, yellow in Pityriasis
versicolor etc.
• Dermascope is hand lens with inbuilt 10-30X magnification
Investigations
• KOH mount test detects fungal infection
• Scraping for scabies
• Patch test and photo patch test detects antigen in case of dermatitis
• Skin biopsy
• Intradermal test includes tuberculin and lepromin test