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The history • 327
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14.1 Functions of the skin
• Protection against physical injury and injurious substances, including
ultraviolet radiation
• Anatomical barrier against pathogens
• Immunological defence
• Retention of moisture
• Thermoregulation
• Calorie reserve
• Appreciation of sensation (touch, temperature, pain)
• Vitamin D production
• Absorption – particularly foetal and neonatal skin
• Psychosexual and social interaction
The deep subcutis contains adipose and connective tissue.
Dermatoses (diseases of the skin) may affect all three layers
and, to a greater or lesser extent, the various functions of the
skin.
Hair
Hair plays a role in the protective, thermoregulatory and sensory
functions of skin, and also in psychosexual and social interactions. There are two main types of hair in adults:
• Vellus hair, which is short and fine and covers most of the
body surface.
• Terminal hair, which is longer and thicker and is found on the
trunk and limbs, as well as the scalp, eyebrows, eyelashes,
and pubic, axillary and beard areas.
Abnormalities in hair distribution can occur when there is
transitioning between vellus and terminal hair types (e.g., hirsutism in women) or vice versa (androgenic alopecia). Hairs
undergo regular asynchronous cycles of growth and, thus, in
health, mass shedding of hair is unusual. Hair loss can occur as a
result of disorders of hair cycling, conditions resulting in damage
to hair follicles (such as scarring inflammatory processes), or
structural (fragile) hair disorders.
Nails
The nail is a plate of densely packed, hardened, keratinised cells
produced by the nail matrix. It serves to protect the fingertip and
aids grasp and fingertip sensitivity. The white lunula at the base
of the nail is the visible distal aspect of the nail matrix (Fig. 14.2).
Fingernail regrowth takes approximately 6 months, and toenail
regrowth 12–18 months.
The history
The possible diagnoses in dermatological conditions are broad
and some diseases have pathognomonic features. Thus, in order
to ensure that your history-taking is focused and relevant, it may
be appropriate to ask to glimpse the lesion or rash before
embarking on detailed enquiry.
14
Common presenting symptom s
These include:
• A rash: scaly, blistering or itchy
• A lump or lesion
• Pruritus (itch)
• Hair loss or excess hair (hirsutism, hypertrichosis)
• Nail changes
Ask:
• When did the lesion appear, or the rash begin?
• Where is the rash/lesion?
Lateral nail fold
(paronychium)
Lunula
Cuticle
Eponychium
A
Fig. 14.2 Structure of the nail. A Dorsal view. B Cross-section.
Distal edge of nail plate
Nail plate
Hyponychium
B
Nail bed
Nail plate
Cuticle
Distal phalanx
Proximal nail fold (paronychium)
Matrix
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• Has the rash spread, or the lesion changed, since its onset?
• Is the lesion tender or painful? Is the rash itchy? Is the itch
intense enough to cause bleeding by scratching or to disturb
sleep, as in atopic eczema and lichen simplex? Are there
blisters?
• Do the symptoms vary with time? For example, the pruritus of
scabies is usually worse at night, and acne and atopic
eczema may show a premenstrual exacerbation.
• Were there any preceding symptoms, such as a sore throat in
psoriasis, a severe illness in telogen effluvium, or a new oral
medication in drug eruptions?
• Are there any aggravating or relieving factors? For example,
exercise or exposure to heat may precipitate cholinergic
urticaria.
• What, if any, has been the effect of topical or oral medications? Self-medication wit h or al antihistamines may
ameliorate urticaria, and topical glucocorticoids may help
inflammatory reactions.
• Are there any associated constitutional symptoms, such as
joint pain (psoriasis), muscle pain and weakness (dermatomyositis), fever, fatigue or weight loss?
• Very importantly, what is the impact of the rash on the individual’s quality of life?
Past medical and drug history
Ask about general health and previous medical or skin conditions; a
history of asthma, hay fever or childhood eczema suggests atopy.
Coeliac disease is associated with dermatitis herpetiformis.
Take a full drug history, including any recent oral or topical
prescribed or over-the-counter medications. Enquire about allergies not just to medicines but also to animals or foods.
Family and social history
14.2 Fitzpatrick scale of skin types
• Type 1: always burns, never tans
• Type 2: usually burns, tans minimally
• Type 3: sometimes burns, usually tans
• Type 4: always tans, occasionally burns
• Type 5: tans easily, rarely burns
• Type 6: never burns, permanent deep pigmentation
The physical examination
Proper assessment of the skin involves all the human senses,
with the exception of taste. Once we have listened to the patient’s history, we look at the rash or lesion, touch the skin, and
occasionally use our sense of smell to diagnose infection and
metabolic disorders such as trimethylaminuria (fish odour syndrome). The increasing use of remote consultations (‘teledermatology’) in clinical practice introduces the risk of certain
aspects of patient assessment being compromised, limiting the
ability to make a precise diagnosis.
Examination of the skin should be performed under conditions
of privacy in an adequately lit, warm room with, when appropriate, a chaperone present (p. 22). The patient should ideally be
undressed to a degree that enables visualisation of all affected
areas of the skin, but allowances should be made for modesty
and religious practices. Routinely, the hair, nails and oral cavity
(p. 213) should be examined, and the regional lymph nodes (p.
36) palpated. Assess skin type using the Fitzpatrick scale (see
Box 14.2 ).
In documenting the appearance of a lesion or rash, use the
correct descriptive terminology (Box 14.3); doing so often helps
crystallise the diagnostic thought processes.
Enquire about occupation and hobbies, as exposure to chemicals may cause contact dermatitis. If a rash consistently improves when a patient is away from work, the possibility of
industrial dermatitis should be considered. Ask about alcohol
consumption and confirm smoking status.
Document foreign travel and sun exposure if actinic damage,
tropical infections or photosensitive eruptions are being considered. The risk of squamous cell and basal cell cancers increases
with total lifetime sun exposure, and intense sun exposures
leading to blistering burns are a risk factor for melanoma. The
susceptibility of an individual to sun-induced damage can be
determined by defining their skin type using the Fitzpatrick scale
(Box 14.2).
Ask about a family history of atopy and skin conditions.
The history of a skin disorder alone rarely enables a definite
diagnosis, with perhaps the occasional exception: an itchy
eruption that resembles a nettle rash, the individual components
of which last less than 24 hours, is very likely to be urticaria; and
an intensely itchy eruption that affects all body areas except the
head (in adults) and is worse in bed at night should be considered to be scabies until proved otherwise.
Distribution of a rash
The distribution of dermatosis can be very informative. Is the
eruption symmetrical? If so, it is likely to have a constitutional
basis, and if not, it may well have an extrinsic cause. This golden
rule has occasional exceptions (such as lichen simplex) but holds
true in the majority of instances.
The pattern of a rash may immediately suggest a diagnosis:
for example, the antecubital and popliteal fossae in atopic
eczema (Fig. 14.3A); the extensor limb surfaces (see
Fig. 14.3B), scalp, nails (see Fig. 3.7A)andumbilicusinpso-
riasis; the flexural aspects of the wrists and the oral mucous
membranes in lichen planus (Fig. 14.4 ); the scalp, al ar grooves
and nasolabial folds in seborrhoeic dermatitis; and the sparing
of covered areas in photosensitive erupt ions. Does the rash
follow a dermatome (as with shingles, see Fig. 7.9), or Langer’s li nes of skin tension (as with pityriasis rosea), or Blaschko
(developmental) lines (as with certai n genetic disorders)? The
localisation of an eruption to fresh scars or tattoos may be a
manifestation of sarcoidosis, a nd the anatomical location may
provide a clue to diagnosis, such as the tendency of erythema
14.3 Descriptive terminology
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The physical examination • 329
Term Definition
Abscess A collection of pus, often associated with signs and
Angioedema Deep swelling (oedema) of the dermis and subcutis
Annular Ring-like
Arcuate Curved
Atrophy Thinning of one or more layers of the skin
Blister A liquid-filled lesion (vesicles and bullae)
Bulla A large blister (>0.5 cm)
Burrow A track left by a burrowing scabies mite
Callus
(callosity)
Circinate Circular
Comedo A blackhead
Crust (scab) A hard, adherent surface change caused by leakage and
Cyst A fluid-filled papular lesion that fluctuates and
Discoid Disc-like
Ecchymosis
(bruise)
Erosion A superficial loss of skin, involving the epidermis; scarring
Erythema Redness of the skin that blanches on pressure
Erythroderma Any inflammatory skin disease that affects >80% of the
Exanthem A rash
Excoriation A scratch mark
Fissure A split, usually extending from the skin surface through
Freckle An area of hyperpigmentation that increases in the
Furuncle A boil
Gyrate Wave-like
Haematoma A swelling caused by a collection of blood
Horn A hyperkeratotic projection from the skin surface
Hyperkeratosis Thickening of the stratum corneum
Ichthyosis Very dry skin
Keratosis A lesion characterised by hyperkeratosis
Lentigo An area of fixed hyperpigmentation
Lichenification Thickening of the epidermis, resulting in accentuation of
symptoms of inflammation (includes boils and carbuncles)
A thickened area of skin that is a response to repeated
friction or pressure
drying of blood, serum or pus
transilluminates
A deep bleed in the skin
is not normally a result
body surface
the epidermis to the dermis
summer months and decreases during winter
skin markings; usually indicative of a chronic eczematous
process
Term Definition
Macule A flat (impalpable) colour change
Milium A keratin cyst
Naevus A localised developmental defect (vascular, melanocytic,
epidermal or connective tissue)
Nodule A large papule (>0.5 cm)
Nummular Coin-shaped
Onycholysis Separation of the nail plate from the nail bed
Papilloma A benign growth projecting from the skin surface
Papule An elevated (palpable) lesion, arbitrarily <0.5 cm in
diameter
Patch A large macule
Pedunculated Having a stalk
Petechiae Pinhead-sized macular purpura
Pigmentation A change in skin colour
Plaque A papule or nodule that in cross-sectional profile is
plateau-shaped
Poikiloderma A combination of atrophy, hyperpigmentation and
telangiectasia
Purpura Non-blanchable redness (also called petechiae)
Pustule A papular lesion containing turbid purulent material (pus)
Reticulate Net-like
Scale A flake on the skin surface, composed of stratum
corneum cells (corneocytes), shed together rather than
individually
Scar The fibrous tissue resulting from the healing of a wound,
ulcer or certain inflammatory conditions
Serpiginous Snake-like
Stria(e) A stretch mark
Targetoid Target-like
Telangiectasia Dilated blood vessels
Ulcer A deep loss of skin, extending into the dermis or deeper;
usually results in scarring
Umbilication A depression at the centre of a lesion
Verrucous Wart-like
Vesicle A small blister (<0.5 cm)
Wheal A transient (<24 hours), itchy, elevated area of skin
resulting from dermal oedema that characterises urticaria
Xerosis Mild/moderate dryness of the skin
14
nodosum (see Fig. 5.7B), pretibial myxoedema (see
Fig. 10.2D) and necrobiosis lipoidica (Fig. 14.5)toinvolvethe
shins.
Morphology of a rash
The morphology (shape and pattern) of a rash is equally important.
Violaceous, polygonal, flat-topped papules, topped by a lacy
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A
A
B
B
Fig. 14.3 Distribution of rash. A Atopic eczema localising to the flexural
aspect of the knees.
patterning (Wickham’s striae), are typical of lichen planus (see
Fig. 14.4). The Koebner (isomorphic) phenomenon, where a
dermatosis is induced by superficial epidermal injury, results in linear
configurations (Fig. 14.6A), and occurs par excellence in psoriasis,
lichen planus, viral warts and molluscum contagiosum. Linear or
angular markings (erythema or scarring) raise the likelihood of
artefactual (self-inflicted) damage to the skin. The presence of
blisters limits the diagnostic possibilities to a relatively small number
of autoimmune (such as dermatitis herpetiformis, pemphigoid (see
Fig. 14.6B) and pemphigus), reactive (including erythema multi-
forme, Stevens–Johnson syndrome and toxic epidermal necrolysis),
infective (such as bullous impetigo and herpes simplex infection)
and inherited (for example, epidermolysis bullosa) disorders. An
annular (ring-like) morphology may be seen in granuloma annulare
(see Fig. 14.6C), sarcoidosis, subacute cutaneous lupus erythematosus, and fungal infections (‘ringworm’). Deeply pigmented skin
types are frequently associated with follicular accentuation of inflammatory processes as well as an increased tendency to scarring
compared to lighter skin types (Fig. 14.7AB).
B Psoriasis involving the extensor aspect of the elbow.
Colour
The vascular contribution to t he colour of a rash can be pivotal
in diagnosis, particularly in light skin types, as redness can
C
Fig. 14.4 Lichen planus. A Discrete flat-topped papules on the wrist. B
Wickham’s striae, visible on close inspection.
striae on the buccal mucosa.
Fig. 14.5 Necrobiosis lipoidica diabeticorum: peripheral erythema and
central yellow-coloured telangiectatic atrophic changes.
C A white lacy network of
A
A
The physical examination • 331
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14
B
B
Fig. 14.7 A Follicular eczema in dark skin. B Keloids due to inflammatory
change in dark skin.
remain wi thin blood vessels; non -blanchabl e redness (purpura) is the re sult of erythrocyte extravasation and en trapment
in the collagen and elastic fibres of the dermis. Erythematous
and purpuric erupti ons usually have very different underlying
causes.
The tint of the erythema may be helpful: a violaceous hue
distinguishes lichen planus; a beefy-red or salmon-pink colour
often typifies psoriasis; and a heliotrope (pink – purple) colour is
C
Fig. 14.6 Rash morphology. A Koebner response in psoriasis. B
Tense bullae (blisters) in pemphigoid.
annulare.
sometimes be difficult to assess in darker skin types. It is not
sufficient to describe a rash as ‘ red’ or ‘pink’; it is essential to
demonstrate whether or not a rash blanches on direct pressure or when the skin is stretched. Blanchable redness (erythema) indicates that the red blood cells causing the colour
C Annular lesions in granuloma
a feature of dermatomyositis, especially on the eyelids.
Macular purpura may be the result of thrombocytopenia or
capillary fragility (see Fig. 10.10D), but palpable purpura (often
painful) usually indicates vasculitis ( Fig. 14.8A) and necessitates exclusion of vasculitic inflammation in other organs.
Purpura elicitable by pinching the skin (‘pinch purpura’)may
be indicative of Amyloidosis light chain (AL) (see Fig. 14.8B).
In those individuals with skin pigmentation at the darker end of
the spectrum, there is the added possibility of increased or
decreased colour (hyper- or hypopigmentation) consequent to
inflammation (Figs 14.9 and 14.10). Disorders characterised by
reduced pigmentation, such as vitiligo (see Fig. 3.10), are more
obvious in dark skin.
A
A
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A
B
Fig. 14.8 Purpura. A Cutaneous vasculitis. B AL (light chain) amyloidosis.
B
Fig. 14.10 Pityriasis versicolor A in Caucasian skin (where affected skin is
lightly pigmented).
hypopigmented).
on applying a shearing force in pemphigus (Nikolsky’s sign), and
B
Fig. 14.9 A Hyperpigmentation within antecubital fossa secondary to
atopic eczema.
the cheek.
B Post-inflammatory hypopigmentation in pityriasis alba on
the very earliest lesions of lichen planus glinting in reflected light
(see Fig. 14.11C).
Scratch marks (excoriations) indicate an itchy rash. In any pruritic
eruption, it is prudent to look specifically for the burrows of scabies
(Fig. 14.12AB)onthehandsandfeet,aswellastotestfordermographism and examine for lymphadenopathy (p. 34), as urticaria
and lymphoma are also important causes of itch.
B in Afro-Caribbean skin (where affected skin is
Specific features
Morphology of lesions
There are also a number of subtle clinical signs that can be of
great diagnostic help in common rashes, such as the distinctive
silver-coloured scale that appears when psoriasis is scratched
(Fig. 14.11AB), the urtication that develops when the pigmented
lesions of urticaria pigmentosa (a form of cutaneous mastocytosis) are rubbed (Darier’s sign), the separation of the epidermis
Lesions should be measured and described according to their
anatomical location, colour, symmetry, surface texture, consistency, demarcation of margin, tenderness and whether they are
freely mobile or attached to underlying tissue (p. 329).
Remember to examine the regional lymph nodes.
The physical examination • 333
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A
C
Fig. 14.11 Specific signs A Psoriasis before surface rubbing. B After surface rubbing. C Lichen planus showing light reflection from small early lesions.
B
14
A B
Fig. 14.12 Scabies burrows. A A tortuous burrow. B Through the dermatoscope, individual mites are visible as small, dark arrowheads.
A
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An irregularly roughened, jagged surface texture is often indicative of sunlight-induced damage (actinic keratosis), whereas the
surface of a seborrhoeic keratosis (Fig. 14.13) has a smoother feel.
The consistency of a lesion is often of diagnostic help: for example,
the firm, button-like quality of a dermatofibroma is very characteristic; neurofibromas are rather soft (see Fig. 3.20); calcium deposits
are hard; and cysts fluctuate and transilluminate. Basal cell carcinoma, the most common malignant tumour, is usually smooth (but
may ulcerate); on inspection, it exhibits a milky, pearlescent colour
(which may glint) and irregular telangiectasia (Fig. 14.14).
It is reassuring to see hair growing out of a pigmented lesion,
as this usually indicates a benign process such as a melanocytic
naevus. However, the possibility that a pigmented lesion is a
malignant melanoma (Fig. 14.15), a potentially life-threatening
cutaneous malignancy, should always be considered. The
acronym ABCDE refers to features in a skin lesion that might
suggest a melanoma:
• Asymmetry
• Border irregularity
• Colour variation
• Diameter >6 mm, Dark or Different
• Evolving or changing
Fig. 14.13 Seborrhoeic keratosis: multiple lesions over the temple
and zygomatic regions.
Fig 14.14 Basal cell carcinoma. A Viewed with the naked eye. B Dermatoscopy highlights distinctive telangiectasia.
Fig. 14.15 Malignant melanoma.
B
A
The physical examination • 335
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Despite its origin from melanocytes, melanoma may occasionally lack pigment (amelanotic melanoma). The ugly duckling sign
refers to pigmented lesions that immediately stand out as being
different, and that therefore should be considered suspicious.
Mouth, hair and nail signs
General physical examination of the skin should always include
the oral cavity, hair and nails.
Inspection of the oral mucous membranes may reveal
diagnostic clues such as the lace-like patterning of lichen
planus (Fig. 14.4C), or the erosions of pemphigus. Gum hygiene may alert to the possibility of a nutritional deficiency such
as scurvy (see Fig 3.19A).
Is there excess hair, either in a male pattern distribution
(hirsutism) or not (hypertrichosis), or hair loss (alopecia)?
Hirsutism may be a marker for hyperandrogenism. Hypertrichosis may be seen in malnutrition states, malignancy and
porphyria cutanea tarda. Discrete, coin-sized areas of hair loss,
with small ‘exclamation mark’ hairs at the periphery, are char -
acteristic of alopecia areata (Fig. 14.16), an autoimmune disorder that may coexist with other autoimmune disorders.
Diffuse, pronounced hair shedding (tel ogen effluvium) may be a
physiological response t o severe illness, major surgical operations, or chil dbirth and may be accompanied by transverse
grooves on the fingernails, which gradually grow out normally
(Beau’s lines; see Fig. 3.7B).
Common abnormalities of the nails associated with underlying
disease are covered on page 26 and in Box 3.3 and Fig. 3.7.
Some rare diseases produce specific nail appearances, such as
the ‘ragged cuticles’ and abnormal capillary nail-bed loops
associated with dermatomyositis (Fig. 14.17AB), and the progressive thickening and opacification of nails in yellow nail syndrome (Fig. 14.18).
14
Fig. 14.16 Alopecia areata.
Fig. 14.17 Nail appearances in systemic diseases. A The typical linear pattern of dermatomyositis with Gottren’s papules on the dorsum of the hand. B
Nail-fold telangiectasia in dermatomyositis, viewed through the dermatoscope.
B
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Fig. 14.18 Yellow nail syndrome in a patient with lymphoedema and
pleural effusions.
Supplementary examination techniques
It is often necessary to complement naked-eye observation of
the skin with assisted examination techniques, such as dermatoscopy, diascopy and Wood’s lamp.
Dermatoscopy
A dermatoscope consists of a powerful light source (polarised or
non-polarised) and a magnifying lens, and enables considerably
more cutaneous anatomical detail to be seen (Fig. 14.19).
Dermatoscopy is particularly useful in the assessment of pigmented lesions but is also often of great help in assessing other
skin tumours, hair disorders and certain infections (scabies, viral
warts and molluscum contagiosum).
Diascopy
The pressure of a glass slide on the skin will compress the
cutaneous blood vessels and blanch the area of contact. If blood
is still visible through the glass, it is because red blood cells have
extravasated (purpura). When granulomatous disorders (such as
sarcoidosis or granuloma annulare) are diascoped, they typically
manifest a green–brown (‘apple jelly’) colour.
Fig. 14.19 Dermatoscope.
fluoresce (such as erythrasma, pityriasis versicolor and some
ringworm infections).
Investigations
After clinical examination, specific investigative techniques may
be necessary in some cases to enable a precise diagnosis.
Skin biopsy
This involves a sample of skin being removed under local
anaesthesia and subjected to histological or immunohistochemical examination in the laboratory. However, clinicopathological correlation is usually necessary.
Mycology
A fungal infection can be confirmed (or refuted) by scraping scale
from the surface of a rash with a scalpel blade, clipping samples
of nail or plucking hair, and undertaking microscopic examination
and culture.
Wood’s lamp
Examination of the skin using an ultraviolet light (Wood’s lamp) is
useful in two clinical situations: it enhances the contrast between
normal skin and under - or over-pigmented epidermis (making
conditions such as vitiligo and melasma easier to see); and it can
identify certain infections by inducing the causative organisms to
Patch testing
Patch testing (Fig. 14.20) is performed to establish whether a
contact allergy is the cause of an individual’s rash. It involves
applying putative allergens to the patient’s skin, leaving the test
patches undisturbed for 2 days, removing them and then reading
the final result after 4 days. A positive result is indicated by an
inflammatory reaction at the site of the patch.
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