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, although sometimes this is neither desirable (e.g. hand warts) nor possible.
The presence of a chaperone, ideally a nurse or a relative, is often sensible, and is essential if examination of the genitalia is necessary. Do not be put off this too easily by the elderly, the stubborn, the shy, or the surroundings.
Sometimes make-up must be washed off or wigs removed. There is nothing more embarrassing than missing the right diagnosis because an important sign has been hidden.
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 der-matitis; 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 pop-liteal fossae.
See if the skin disease is localized, universal or sym-metrical. Depending on the disease suggested by the morphology, you may want to check special areas, like the feet in a patient with hand eczema, or the gluteal cleft in a patient who might have psoriasis. Examine as much of the skin as possible. Look in the mouth and remember to check the hair and the nails . Note negative as well as positive findings, e.g. the way the shielded areas are spared in a photosensitive dermatitis (see Fig. 16.7). Always keep your eyes open for incidental skin cancers which the patient may have ignored.
After the distribution has been noted, next define the morphology of the primary lesions. 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?
Most types of primary lesion have one name if small, and a different one if large. The scheme is summarized in Table 3.2.
There are many reasons why you should describe skin diseases properly.
• Skin disorders are often grouped by their morpho-logy. Once the morphology is clear, a differential diagnosis comes easily to mind.
• If you have to describe a condition accurately, you will have to look at it carefully.
• You can paint a verbal picture if you have to refer the patient for another opinion.
• You will sound like a physician and not a homoeopath.
• You will be able to understand the terminology of this book.
Erythema is redness caused by vascular dilatation.
A papule is a small solid elevation of skin, less than
0.5 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 of altered colour or texture.
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 some-times 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 evanes-cent 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 oedemaextending 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 or can be palpated.
A tumour is harder to define as the term is based more correctly on microscopic pathology than on clinical morphology. We keep it here as a convenient term to describe an enlargement of the tissues by normal or pathological material or cells that form a mass, usually more than 1 cm in diameter. Because the word ‘tumour’ can scare patients, tumours may courteously be called ‘large nodules’, especially if they are not malignant.
A papilloma is a nipple-like projection from the skin.
Petechiae are pinhead-sized macules of blood in theskin.
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 (diascopy).
An ecchymosis is a larger extravasation of blood into the skin.
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 a dilated 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 smallcutaneous blood vessels.
Poikiloderma is a combination of atrophy, reticu-late hyperpigmentation and telangiectasia.
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, but is 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 struc-tures are permanently replaced by fibrous tissue.
Atrophy is a thinning of skin caused by diminutionof the epidermis, dermis or subcutaneous fat. When the epidermis is atrophic it may crinkle like cigarette paper, appear thin and translucent, and lose normal surface markings. Blood vessels may be easy to see in both epidermal and dermal atrophy.
Lichenification is an area of thickened skin withincreased 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 surroundingskin, can develop after lesions heal.
Having identified the lesions as primary or secondary, adjectives can be used to describe them in terms of their other features.
• Colour (e.g. salmon-pink, lilac, violet).
• Sharpness of edge (e.g. well-defined, ill-defined).
• Surface contour (e.g. dome-shaped, umbilicated, spire-like; Fig. 3.2).
• Geometric shape (e.g. nummular, oval, irregular, like the coast of Maine).
• Texture (e.g. rough, silky, smooth, hard).
• Smell (e.g. foul-smelling).
• Temperature (e.g. hot, warm).
Dermatologists also use a few special adjectives
which warrant definition.
• 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.
To describe a skin lesion, use the term for the primary
lesion as the noun, and the adjectives mentioned above to define it. For example, the lesions of psoriasis may appear as ‘salmon-pink sharply demarcated nummular plaques covered by large silver polygonal scales’.
Try not to use the terms ‘lesion’ or ‘area’. Why say ‘papular lesion’ when you can say papule?
It is almost as bad as the ubiquitous term ‘skin rash’. By the way, there are very few diseases that are truly ‘maculopapular’. The term is best avoided except to describe some drug eruptions and viral exanthems. Even then, the terms ‘scarlatiniform’ (like scarlet fever apunctate, slightly elevated papules) or ‘morbilliform’ (like measlesaa net-like blotchy slightly elevated pink exanthem) are more helpful.
After unravelling the primary and secondary lesions, look for arrangements and configurations that can be, for example, discrete, confluent, grouped, annular, arcuate or dermatomal (Fig. 3.3). Note that while individual lesions may be annular, several individual lesions may arrange themselves into an annular con-figuration. Terms like annular, and other adjectives discussed under the morphology of individual lesions, can apply to their groupings too. The Köbner or iso-morphic phenomenon is the induction of skin lesions by, and at the site of, trauma such as scratch marks or operative incisions.