Dignosis of skin diseases

د. محمد جواد العبد الله

2017\10\11
DIAGNOSIS OF SKIN DISEASES

HISTORY:

1. Age, sex, race, residency, occupation.
2. Duration of onset and course of the lesion.
3.relationship of skin lesions to:
- season
- traveling
- drug ingestion
- heat and cold
- previous treatment
- occupation
- Menses and pregnancy.
4. Skin symptoms: pruritis, pain and parasthesia.
5. Constitutional symptoms.
6. System review.
7. Family history.


PHYSICAL EXAMINATION:
1. Appearance of the patient: toxic, well, and uncomfortable.
2. Vital signs: pulse, respiration, temperature.
3. Skin lesions:
- Type
- Shape
- Arrangement
- Distribution
- Color
- Margin
- Palpation.
4. Hair and nails.
5. Mucous membranes.

TYPES OF THE LESIONS:

1. PRIMARY (BASIC) LESIONS:
- Macule: circumscribed flat discoloration of the skin less than 0.5 cm diameter.
- Patch: flat lesion more than 0.5 cm.
- Papule: solid elevated lesion less than 0.5 cm.
- Plaque: elevated lesion more than 0.5 cm.
- Nodule: palpable solid lesion, deep in the dermis or subcutaneous tissue.
- Vesicle: circumscribed elevated lesion, containing free fluid, less than 0.5 cm.
- Bulla: elevated lesion with free fluid, more than 0.5 cm.
- Blister: includes both vesicles and bullae.
- Wheal (hive): transient edematous elevation in the skin, resulting from upper dermal edema. It is the primary lesion of urticaria.
- Pustule: circumscribed elevated lesion, containing a purulent exudates.
- petechiae: circumscribed deposition of blood elements (haemosiderin) of less than 0.5 cm.
- purpura: deposition of blood elements more than 0.5 cm.
-Ecchymosis :is a larger extravasation of blood into the skin
- Telengiectasia: permanent dilatation of superficial blood vessels.
- comedone: plug of sebum and keratinous material lodged in the opening of hair follicle. It is either opened (black) or closed (white) comedones. It is the primary lesion of acne vulgaris.
Burrow : linear or curvilinear papule, with some scaling, caused by a scabies mite.


SECONDARY (SEQUENTIAL) LESIONS:
Scale: shedded desquamating epidermal cells.
Crust: dried scales, sebum and purulent exudates on the skin surface. It is the hallmark of any pyogenic infection.
Fissure: linear cut in the epidermis and dermis, with sharply defined vertical edges.
Erosion: superficial loss of the epidermis, that heals without scar.
Ulcer: destruction of the epidermis and upper papillary dermis, that heals with scar formation.
Scar: abnormal formation of connective tissue after deep skin damage. It implies dermal injury.
Excoriation: linear scratch marks on the skin.
Atrophy: depression in the skin surface, resulting from thinning of the epidermis or dermis.
Lichenification: thickening of the skin surface with hyperpigmentation and exentuation of skin lines. It is due to chronic severe itching.

COLOR OF LESIONS:

Skin lesions could present with many colors like white, red, pink, violaceous, brown, black, blue, grey, yellow, purpuric and others.

PALPATION OF LESIONS:

consistency ex. Soft, firm, hard, fluctuant, board like
temperature whether cold or hot.
Mobility
Tenderness
Depth
Diascopy: applying pressure on the skin by a finger or glass slide
will abolish the erythema, while purpura persists.


SHAPE OF LESIONS:
Whether round, oval, polygonal, polycyclic, iris like, annular

MARGIN OF LESIONS:

Ill defined or well defined.

ARRANGEMENT OF MULTIPLE LESIONS:

grouped: ex. Herpetiform, zosteriform, aciform, annular, reticulated (network like), linear (may be caused by Kobner phenomenon).
Kobner phenomenon: is appearance of new skin lesion of same disease at the site of trauma , ex. Psoriasis, lichen planus, vitiligo, viral warts, eczema, and mulloscum contagiosum.
Disseminated lesions may be scattered, discrete or diffuse.

DISTRIBUTION OF LESIONS:

extent: ex. Isolated, localized, generalized or universal.
Pattern: random, symmetrical or follicular distribution, on exposed areas, sites of pressure, intertriginous areas.

LABORATORY AND SPECIAL EXAMINATIONS:

1. SKIN BIOPSY (DERMATOPATHOLOGY):
Many techniques are available to perform skin biopsy which is usually taken from fully developed lesion that should be undamaged or modified by scratching or topical treatment. One exception is the vesicullobullous diseases in which the biopsy should be taken from early lesion that is unruptured, and not complicated by secondary pyogenic infection. The biopsy could be studied using:

light microscopy.

Immunofluroscence.
Immunohistochemical stains.
Electron microscopy:


EPIDERMAL CHANGES:
hyperkeratosis: increased thickness of stratum corneum.
Parakeratosis: increased thickness of stratum corneum with retained nuclei.
Hypergranulosis: increased thickness of stratum granulosum.
Acanthosis: increased thickness of stratum spinosum.
Spongiosis: accumulation of extra cellular fluid within the epidermis with resultant separation of keratinocytes (i.e. intercellular edema).
Acantholysis: separation of cells due to destruction of the intercellular bridges (desmosomes).

Liquefaction (hydropic) degeneration of basal layer: formation of vacuolar spaces between and beneath the basilar keratinocytes.

DERMAL CHANGES:

type of inflammatory infiltrate (neutrophilic, lymphocytic or eosinophilic).
Change in dermal thickness.
Presence of leucocytoclastic vasculitis which involve small blood vessels with neutrophilic infiltrate, the nuclei of which are fragmented (i.e. called nuclear dust) and deposition of fibrin.

2. MICROSCOPICAL EXAMINATION OF LESIONS:

direct microscopical examination:
yeasts and fungi: 10 % KOH examination.
Bacteria: Grams stain.
Spirochetes: dark field examination.
Parasites: scabie mite from the skin burrows.
Viruses: Tzanck smear is microscopical examination of cells from the base of viral vesicles, after being stained with Giemsas or Wrights stain.


Culture for bacteria, fungi

3. LABORATORY EXAMINATION OF BLOOD:

- Bacteriologic: culture.
- Serologic: ex. Serological tests for syphilis (STS) or antinuclear antibodies (ANA).

4. IMAGING ex. XR, US, CT, MRI

5. URINE ANALYSIS.

6. STOOL EXAMINAION for:

- Occult blood
- Ova and parasites
- Porphyrines.

7. PATCH TEST for allergic contact sensitivity.

8. ACETOWHITENING: the application of 5% acetic acid to the anogenital area results in whitening of subclinical genital warts.

9. Woods light examination:

It is a UV light in the range of 360 nm.


Indications of Woods light:
Diagnosis, follow up and screening of taenia capitis, giving (greenish florescence).
Taenia versicolor (golden yellow).
Erythrasma (coral red).
Pseudomonas infection (green).
Porphyria (red color of teeth).
Vitiligo (milky white).
Differentiation between dermal and epidermal types of melasma.
Differentiation between nits and scales in patients with pediculosis capitis.