diagnosis of skin diseases word

Diagnosis of skin disorders

History
History of present skin condition
Duration
Site at onset, details of spread
Itch
Burning
Pain
Wet, dry, blisters
Exacerbating factors
Gowth
Bleeding

General health at present

Ask about fever

Past history of skin disorders

Past general medical history
Ask about asthma and hay fever


Family history of skin disorders
If positive, the disorder or the tendency to have it may be inherited. Sometimes family members may be exposed to a common infectious agent, scabies, chemical.

Social and occupational history

Hobbies, Outdoor versus indoor, Travels abroad, Relationship of rash to work and holidays, Alcohol intake.

Drugs used to treat present skin condition

Whether topical or systemic, physician prescribed or patient initiated

Drugs prescribed for other disorders

Including those taken before onset of skin disorder

Examination

To examine the skin properly, the lighting must be uniform and bright. Daylight is best. The patient should usually undress so that the whole skin can be examined,. Sometimes make-up must be washed off .
1.Distribution
A dermatological diagnosis is based both on the distribution of lesions and on their morphology and configuration. For example, an area of seborrhoeic dermatitis may look very like an area of atopic dermatitis, but the key to diagnosis lies in the location. Seborrhoeic dermatitis affects the scalp, forehead, eyebrows, nasolabial folds and central chest; atopic dermatitis typically affects the antecubital and popliteal fossae. See if the skin disease is localized, universal or symmetrical. Symmetry implies a systemic origin, whereas unilaterality or asymmetry implies an external cause. Look in the mouth and remember to check the hair and the nails.
2.Morphology
Many skin diseases have a characteristic morphology, but scratching, ulceration and other events can change this. The rule is to find an early or ‘primary’ lesion and to inspect it closely. What is its shape? What is its size? What is its colour? What are its margins like? What are the surface characteristics? What does it feel like?
Terminology of lesions
Primary lesions
Erythema is redness caused by vascular dilatation.
A papule is a small solid elevation of skin, less than0.5 cm in diameter
.A plaque is an elevated area of skin greater than 2 cm in diameter but without substantial depth.
A macule is a small flat area, less than 5 mm in diameter, of altered colour or texture.
A patch is a large macule.
A vesicle is a circumscribed elevation of skin, less than 0.5 cm in diameter,and containing fluid.
A bulla is a circumscribed elevation of skin over 0.5 cm in diameter and containing fluid.
A pustule is a visible accumulation of pus in the skin.
An abscess is a localized collection of pus in a cavity, more than 1 cm in diameter. Abscesses are usually nodules, and the term ‘purulent bulla’ is sometimes used to describe a pus-filled blister that is situated on top of the skin rather than within it.
A wheal is an elevated white compressible evanescent area produced by dermal oedema. It is often surrounded by a red axon-mediated flare. Although usually less than 2 cm in diameter, some wheals are huge.
Angioedema is a diffuse swelling caused by oedema extending to the subcutaneous tissue.
A nodule is a solid mass in the skin, usually greater than 0.5 cm in diameter, in both width and depth, which can be seen to be elevated (exophytic) or can be palpated (endophytic).
A tumour is harder to define as the term is based more correctly on microscopic pathology than on clinical morphology.
A papilloma is a nipple-like projection from the skin.
Petechiae are pinhead-sized macules of blood in the skin.
The term purpura describes a larger macule or papule of blood in the skin. Such blood-filled lesions do not blanch if a glass lens is pushed against them
An ecchymosis (bruise) is a larger extravasation of blood into the skin and deeper structures.
A haematoma is a swelling from gross bleeding.
A burrow is a linear or curvilinear papule, with some scaling, caused by a scabies mite.
A comedo is a plug of greasy keratin wedged in adilated pilosebaceous orifice. Open comedones are ‘blackheads’. The follicle opening of a closed comedo is nearly covered over by skin so that it looks like a pinhead-sized, ivory-coloured papule.
Telangiectasia is the visible dilatation of small cutaneous blood vessels.
Poikiloderma is a combination of atrophy, reticulate hyperpigmentation and telangiectasia.
Horn is a keratin projection that is taller than it is broad.
Erthyroderma is a generalized redness of skin that may be scaling (exfoliative erythroderma) or smooth.
Secondary lesions
These evolve from primary lesions.
A scale is a flake arising from the horny layer.
A keratosis is a horn-like thickening of the stratum corneum.
A crust may look like a scale, composed of dried blood or tissue fluid.
An ulcer is an area of skin from which the whole of the epidermis and at least the upper part of the dermis has been lost. Ulcers may extend into subcutaneous fat, and heal with scarring.
An erosion is an area of skin denuded by a complete or partial loss of only the epidermis. Erosions heal without scarring.
An excoriation is an ulcer or erosion produced by scratching.
A fissure is a slit in the skin.
A sinus is a cavity or channel that permits the escape of pus or fluid.
A scar is a result of healing, where normal structures are permanently replaced by fibrous tissue.
Atrophy is a thinning of skin caused by diminution of the epidermis, dermis or subcutaneous fat.
Lichenification is an area of thickened skin with increased markings.
A stria (stretch mark) is a streak-like linear atrophic pink, purple or white lesion of the skin caused by changes in the connective tissue.
Pigmentation, either more or less than surrounding skin, can develop after lesions heal.
Other term can be used for description :
Nummular means round or coin-like.
Annular means ring-like.
Circinate means circular.
Arcuate means curved.
Discoid means disc-like.
Gyrate means wave-like.
Retiform and reticulate mean net-like.
Targetoid means target-like or ‘bull’s eye’.
Polycyclic means formed from coalescing circles,or incomplete rings.


3.Configuration
Arrangements and configurations can be as discrete, confluent, grouped, annular, arcuate, segmental or dermatomal . Individual lesions may be annular, several individual lesions may arrange themselves into polycyclic configuration. The Köbner or isomorphic phenomenon is the induction of skin lesions by, and at the site of, trauma such as scratch marks or operative incisions.
Special tools and techniques
A magnifying lens subtle changes in the skin become more apparent when enlarged.
A Wood’s light. This is a source of ultraviolet light from which virtually all visible rays have been excluded by a Wood’s (nickel oxide) filter. Fluorescence is seen in some fungal infections , erythrasma and Pseudomonas infections. Some subtle disorders of pigmentation can be seen more clearly under Wood’s light (e.g. the pale patches of tuberous sclerosis,low-grade vitiligo and pityriasis versicolor, and the darker café au lait patches of neurofibromatosis). The urine in hepatic cutaneous porphyria often fluoresces coral pink, even without solvent extraction of the porphyrins .
Diascopy is the name given to the technique in which a glass slide or clear plastic spoon is pressed on vascular lesions to blanch them and verify that their redness is caused by vasodilatation and to unmask their underlying colour. Diascopy is also used to confirm the presence of extravasated blood in the dermis (petechia and purpura, the appearance of which do not change on pressure).
Photography, helps to record the baseline appearance of a lesion or rash, so that change can be assessed objectively at later visits.
Dermatoscopy . Many structures can be identified that are not visible to the naked eye. The lesion is covered with ultrasound gel, mineral oil, alcohol or water and then illuminated and observed at 10×magnification with a hand-held dermatoscope. The gel or fluid eliminates surface reflection and makes the horny layer translucent so that pigmented structures in the epidermis and superficial dermis, and the superficial vascular plexus , can be assessed. A dermatoscope can also be used to identify scabies mites in their burrows and, used without oil, for diagnosing abnormalities of hair shafts.
Skin tests
Potassium hydroxide preparations. If a fungal infection is suspected, scales or plucked hairs can be dissolved in an aqueous solution of 20% potassium hydroxide (KOH). The scale from the edge of a scaling lesion is vigorously scraped on to a glass slide with a No. 15 scalpel blade or the edge of a second glass slide. Other samples can include nail clippings, the roofs of blisters, hair pluckings and the contents of pustules when a candidal infection is suspected. A drop or two of the KOH solution is run under the cover slip. After 5 –10 min the mount is examined under a microscope with the condenser lens lowered to increase contrast. Nail clippings take longer to clear – up to a couple of hours.
Cytology (Tzanck smear). Cytology can aid the diagnosis of viral infections such as herpes simplex and zoster, and of bullous diseases such as pemphigus. A blister roof is removed and the cells from the base of the blister are scraped off with a No. 10 or 15 surgical blade. These cells are smeared on to a microscope slide, air-dried and fixed with methanol. They are then stained with Giemsa, toluidine blue or Wright’s stain. Acantholytic cells are seen in pemphigus, and multinucleated giant cells are diagnostic of herpes simplex or varicella zoster infections.
Patch tests. Patch tests are invaluable in detecting the allergens responsible for allergic contact dermatitis .A patch test involves applying a chemical to the skin and then watching for dermatitis to develop 48 –96 h later. Standard dilutions of the common antigens in appropriate bases are available commercially .The test materials are applied to the back under aluminium discs or patches; the occlusion encourages penetration of the allergen. The patches are left in place for 48 h and then, after careful marking,are removed. The sites are inspected 10 min later, again 2 days later and sometimes even later if doubtful reactions require further assessment. The test detects type IV delayed hypersensitivity reactions.
NT Not tested.
−No reaction.
±Doubtful reaction (minimal erythema).
+Weak positive reaction (erythema and may be papules).
++Strong reaction (palpable erythema and/or vesicles).
+++Extreme reaction (intense palpable erythema, coalescing vesicles and/or bullae).
IR Irritant reaction (variable, but often sharply circumscribed, with a glazed appearance and increased skin markings)
Prick testing. It detects immediate (type I) hypersensitivity and patients should not have taken systemic antihistamines for at least 48 h before the test. Commercially prepared diluted antigens and a control are placed as single drops on marked areas of the forearm. The skin is gently pricked through the drops using separate sterile fine ( 25 gauge, or smaller ) needles. The prick should not cause bleeding. The drops are then removed with a tissue wipe. After 10 min the sites are inspected and the diameter of any wheal measured and recorded. A result is considered positive if the test antigen causes a wheal of 4 mm or greater and the control elicits a negligible reaction.
Skin biopsy
Biopsy (from the Greek bios meaning ‘life’ and opsis ‘sight’) of skin lesions is useful to establish or confirm a clinical diagnosis. A piece of tissue is removed surgically for histological examination and sometimes for other tests (e.g. culture for organisms). Skin biopsies may be incisional, when just part of a lesion is removed for laboratory examination, or excisional, when the whole lesion is cut out. Excisional biopsy is preferable for most small lesions (up to 0.5 cm diameter) but incisional biopsy is chosen when the partial removal of a larger lesion is adequate for diagnosis, and complete removal might leave an unnecessary and unsightly scar. Ideally, an incisional biopsy should include a piece of the surrounding normal skin.
Local anaesthetic. Lidocaine (lignocaine) 1–2% is used. Sometimes adrenaline (epinephrine) 1 : 200 000 is added. This causes vasoconstriction, reduced clearance of the local anaesthetic and prolongation of the local anaesthetic effect. Plain lidocaine should be used on the fingers ,toes and the penis as the prolonged vasoconstriction produced by adrenaline can be dangerous here. It is wise to avoid local anaesthesia during early pregnancy and to delay non-urgent procedures until after the first trimester. Infiltration of the local anaesthetic into the skin under and around the area to be biopsied is the most widely used method. If the local anaesthetic is injected into the subcutaneous fat, it will be relatively pain-free, will produce a diffuse swelling of the skin and will take several minutes to induce anaesthesia. Intradermal injections are painful and produce a discrete wheal associated with rapid anaesthesia.
Scalpel biopsy. This provides more tissue than a punch biopsy. It can be used routinely, but is especially useful for biopsying disorders of the subcutaneous fat, for obtaining specimens with both normal and abnormal skin for comparison and for removing small lesions (excision biopsy). After selecting the lesion for biopsy, an elliptical piece of skin is excised. The specimen should include the subcutaneous fat. Removing the specimen with forceps may cause crush artefact, which can be avoided by lifting the specimen with either a Gillies hook or a syringe needle. The wound is then sutured; firm compression for 5 min stops oozing. Non-absorbable 3/0 sutures are used for biopsies on the legs and back, 5/0 for the face and 4/0 for elsewhere. Stitches are usually removed from the face in 4 days, from the anterior trunk and arms in 7 days, and from the back and legs in 10 days.
Punch biopsy. The skin is sampled with a small (3 – 4 mm diameter) tissue punch. Lidocaine 1% is injected intradermally first, and a cylinder of skin is incised with the punch by rotating it back and forth. The skin is lifted up carefully with a needle or forceps and the base is cut off at the level of subcutaneous fat. The defect is cauterized or repaired with a single suture. If a lesion is superficial, a shave biopsy may be preferred .