White : Diseases of the Skin - Approach to the Patient

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Gary M. White & Neil H. Cox

Diseases of the Skin

2	Approach to the Patient

EXAMINATION OF THE SKIN

Examination of the skin should be performed in an environment with appropriate privacy and with good illumination. Mobile lighting is required for close-up inspection and to side-light the skin, a useful maneuver in assessing texture and minor degrees of elevation above the skin surface. A good examination light is important for examination of the mouth, and a torch to test for transillumination. A hand lens is often useful for detailed examination, and a ruler is essential for recording lesion sizes.Other tools and techniques of value are listed below.

Ideally, the entire skin should be examined as, even if not obviously pertinent for localized lesions, there may be important incidental findings. It may also provide unexpected clues to the diagnosis of the presenting condition. Similarly, it is sometimes crucial, and often helpful, to examine the mouth and specialized skin structures such as the nails. However, performing a full skin examination in all patients routinely may not always be feasible. It can be time-consuming to prepare the patient, to perform the examination, and to explain incidental findings that may have no significance; additionally, some patients are embarrassed by the prospect of a full skin examination that they have not anticipated (e.g. if they have presented with a simple lesion on an arm). In practice, whether it is possible to routinely perform full skin examination is likely to be largely determined by the expectations and volume demands of the healthcare system in which the practitioner works. It may also be influenced by the likely yield of significant lesions; for example, it is potentially more valuable in areas of high melanoma prevalence than in areas of low prevalence.

General examination

Many factors of potential diagnostic benefit may be apparent even before any formal examination. Thus arthritis, jaundice, thyroid disease, etc. may all be appreciated at a distance. The same applies to some dermatoses on the face, and general cutaneous features, such as overt solar damage, are readily visible and appreciated before a more detailed examination. Other physical signs may be presented during the consultation (Fig.2.16). Olfactory stimuli such as alcohol, or smell from ulcers, may also be very apparent.

The extent of the general medical examination required will obviously vary depending on the diagnostic area, and will not be detailed here. The body site affected may be specifically important (Figs 2.17 and 2.18), and may affect the appearance of some eruptions, for example erythematous scaling rashes such as psoriasis occurring in the flexures have a brighter red color and may lack scale compared with their morphology at other sites. Similarly, some rashes or localized lesions have a particular predilection for specific sites (see later in this chapter)

Examination modalities and special techniques

Examination of skin lesions should determine the shape, elevation, symmetry, morphology of the border, color, vascularity, and presence of hyperkeratosis or crusting. The terminology for the shapes and patterns is described in Chapter 1. Simple visual inspection of the skin can be significantly enhanced by a variety of simple techniques, and by using other sensory modalities, such as touch. Some of these, all of which are commonly performed as part of clinical examination, are listed briefly. Additional tests that require less routine equipment, or that have a laboratory component, are discussed separately.

Figure. 2.19 (a,b) Stretching the skin reveals features that may not initially be apparent. Close up, it reduces vascularity and enables other colors to be seen. In this case, the characteristic sparing of creases (the deckchair sign) of a disorder known as papuloerythroderma (Ofuji disease) is made apparent.

Figure. 2.20 (a,b) Picking the skin is vital to evaluate some crusted conditions. In this case, an apparently large nodule was simply lifted off and demonstrated to be a large heap of infected crust overlying a small area of benign granulation tissue.

Palpation

It is rare for dermatologists to diagnose a rash or localized lesion without touching it (Figs 2.14 and 2.19). Simple palpation of the skin will give information about the following.

•	Surface texture and quality of scaling—texture of scaling differs between dermatoses, and the generally dry skin of atopic dermatitis is best assessed by touch.
•	Deeper texture—is the lesion firm or softfi
•	Thickness of lesions—particularly applied to nodular lesions.
•	Skin temperature—for example increased in infection and several inflammatory conditions, but typically decreased over chilblains.

There are several useful extensions of simple palpation, which include the following.

•	Squeezing—for example, tethered dermal nodules such as dermatofibromas will dimple into the skin when squeezed. Some lesions may express pus or mucin when squeezed.
•	Picking the crust off moist skin lesions—this is useful for visualization of the base (Fig. 2.20); a diagnosis can rarely be made when the only visible feature is crust.
•	Linear pressure and rubbing—linear stroking of the skin may elicit a dermographic response in urticaria (Ch. 9), and rubbing the skin can be helpful in diagnosis of urticaria pigmentosa by producing the Darier sign (Fig. 2.21).
•	Scratching a scaly rash—this may demonstrate the fine, bran-like scale of pityriasiform processes, or the striking silvery scaling of psoriasis

Figure. 2.21 Darier sign. Rubbing the skin lesions of urticaria pigmentosa and other forms of mastocytosis causes degranulation of mast cells. The release of histamine and other inflammatory mediators produces perilesional erythema or a weal and flare reaction.

Figure. 2.22 ( a , b ) Diascopy. This technique compresses intravascular blood out of skin lesions to demonstrate other color changes, or to demonstrate extravasated blood. It is usually performed using a glass microscope slide or, with a greater degree of safety, with a stiff strip of colorless plastic. In this case, diascopy of a Spitz nevus reveals the underlying brownish color of melanin that is otherwise largely obscured by the prominent vascular component.

Figure. 2.23Wood's light examination. In this case demonstrating the yellow fluorescence of pityriasis versicolor, although in normal lighting the lesions would appear pale brown.

Paring lesions

Some keratinized lesions have to be scalpel-pared to confirm a diagnosis. This particularly applies to the differential diagnosis between warts and corns on the sole of the foot; the former have small, dark dots due to thrombosed vessels when the surface is pared, whereas corns have a small, pearly, central nodule of compact keratin.

Diascopy

This is the use of a firm, colorless translucent strip to compress blood out of the skin and to enhance the visibility of other colors (Fig.2.22). It is particularly valuable in diagnosis of granulomatous disorders, which have a residual yellowish brown color, and to detect melanin pigmentation in highly vascularized nevi. It will also distinguish between intravascular and extravasated blood; however, there are some pitfalls to this technique when evaluating tiny spots of possible purpura, as some small and tortuous angiomas are unable to be emptied of their blood content by the rather diffuse compression that is applied

Skin-surface microscopy

Several instruments are now available for skin microscopy (dermoscopy). Traditionally, this was used for examination of abnormal nail fold capillaries in connective tissue disorders, but more recently has been used in the diagnosis of pigmented lesions, especially in the differential diagnosis between nevi and melanoma. There are numerous specialist publications on this topic and the many diseases that it can help to diagnose; for example angiomas and basal cell carcinoma have features that are often characteristic, and scabies mites can be visualized.

Wood’s light

Wood's light is a long-wavelength (around 364nm) UV light, which is useful in several areas in dermatology (Fig.2.23). Examples of different types of use include the following.

•	Infections—it is used to demonstrate fluorescence in some infections (usually for cat and dog type of scalp ringworm, erythrasma, and pityriasis versicolor, but Pseudomonas spp. also fluoresce).
•	Porphyria—the urine in porphyria cutanea tarda fluoresces reddish pink.
•	Pigmentation—it accentuates epidermal pigmentation, and is therefore useful in the diagnosis of some pigmentary disorders. For example, the pale areas of vitiligo (loss of epidermal melanocytes) are exaggerated under Wood's light, whereas the pale skin of nevus anemicus (which is due to vasoconstriction, with normal epidermal melanization) becomes invisible.
•	Natural pigments—in chromhidrosis, patients notice coloured sweat; this is due to lipofuscins in the sweat, which fluoresce green (see Ch. 23).