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
• terminal hair, which is longer and thicker, and is found on
trunk and limbs, as well as 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 (for example,
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 purposeful removal in trichotillomania),
or structural (fragile) hair disorders.
The nail is a plate of densely packed, hardened, keratinised cells
produced by the nail matrix. It serves to protect the fingertip
and aid 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 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.
• a rash: scaly, blistering or itchy
• hair loss or excess hair (hirsutism, hypertrichosis)
• When did the lesion appear or the rash begin?
• Has the rash spread, or the lesion changed, since its
• 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
• 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
• 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
• Are there any aggravating or relieving factors? For
example, exercise or exposure to heat may precipitate
• What, if any, has been the effect of topical or oral
medications? Self-medication with oral antihistamines may
ameliorate urticaria, and topical glucocorticoids may help
• Are there any associated constitutional symptoms,
such as joint pain (psoriasis), muscle pain and
weakness (dermatomyositis), fever, fatigue or
• Very importantly, what is the impact of the rash on the
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 medication. Enquire about allergies
not just to medicines but also to animals or foods.
Fig. 14.2 Structure of the nail. A Dorsal view. B Cross-section.
Proximal nail fold (paronychium)
286 • The skin, hair and nails
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
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
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.
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
Examination of the skin should be performed under conditions
of privacy in an adequately lit, warm room with, when appropriate,
a chaperone present (p. 20). The patient should ideally be
undressed to their underwear. Routinely, the hair, nails and oral
cavity (p. 187) should be examined, and the regional lymph
nodes (p. 33) palpated. Assess skin type using the Fitzpatrick
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.
The distribution of a 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. Its application will
almost always prevent the common misdiagnosis of ‘bilateral
cellulitis’ (bacterial infection) of the legs, which in actuality is
usually lipodermatosclerosis or varicose eczema; bacteria are
not known for their sense of symmetry!
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, scalp, nails and umbilicus
in psoriasis (Fig. 14.3B); the flexural aspects of the wrists and
the oral mucous membranes in lichen planus; the scalp, alar
grooves and nasolabial folds in seborrhoeic dermatitis; and the
sparing of covered areas in photosensitive eruptions. Does the
rash follow a dermatome (as with shingles), or Langer’s lines of
skin tension (as with pityriasis rosea), or Blaschko (developmental)
lines (as with certain genetic disorders)? The localisation of an
eruption to fresh scars or tattoos may be a manifestation of
sarcoidosis, and the anatomical location may provide a clue to
diagnosis, such as the tendency of erythema nodosum, pretibial
myxoedema and necrobiosis lipoidica (Fig. 14.4) to involve
The morphology (shape and pattern) of a rash is equally
important. Violaceous, polygonal, flat-topped papules, topped
by a lacy patterning (Wickham striae), are typical of lichen planus
(Fig. 14.5). 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
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
Fig. 14.3 Distribution of rash. A Atopic eczema localising to the
flexural aspect of the knees. B Psoriasis involving the extensor aspect of
The physical examination • 287
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 (Fig. 14.6B) and pemphigus), reactive (including
Abscess A collection of pus, often associated with signs
and symptoms of inflammation (includes boils and
Angioedema Deep swelling (oedema) of the dermis and
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) A thickened area of skin that is a response to
Crust (scab) A hard, adherent surface change caused by
leakage and drying of blood, serum or pus
Cyst A fluid-filled papular lesion that fluctuates and
Erosion A superficial loss of skin, involving the epidermis;
scarring is not normally a result
Erythema Redness of the skin that blanches on pressure
Erythroderma Any inflammatory skin disease that affects >80%
Fissure A split, usually extending from the skin surface
through the epidermis to the dermis
Freckle An area of hyperpigmentation that increases in the
summer months and decreases during winter
Haematoma A swelling caused by a collection of blood
Horn A hyperkeratotic projection from the skin surface
Hyperkeratosis Thickening of the stratum corneum
Keratosis A lesion characterised by hyperkeratosis
Lentigo An area of fixed hyperpigmentation
Lichenification Thickening of the epidermis, resulting in
accentuation of skin markings; usually indicative of
Macule A flat (impalpable) colour change
Naevus A localised developmental defect (vascular,
melanocytic, epidermal or connective tissue)
Nodule A large papule (>0.5 cm)
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
Petechiae Pinhead-sized macular purpura
Pigmentation A change in skin colour
Plaque A papule or nodule that in cross-sectional profile is
Poikiloderma A combination of atrophy, hyperpigmentation and
Purpura Non-blanchable redness (also called petechiae)
Pustule A papular lesion containing turbid purulent material
Scale A flake on the skin surface, composed of stratum
corneum cells (corneocytes), shed together rather
Scar The fibrous tissue resulting from the healing of a
wound, ulcer or certain inflammatory conditions
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
Vesicle A small blister (<0.5 cm)
Wheal A transient (<24 hours), itchy, elevated area of
skin resulting from dermal oedema that
Xerosis Mild/moderate dryness of the skin
erythema multiforme, 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 (Fig. 14.6C), subacute cutaneous lupus
erythematosus, and fungal infections (‘ringworm’).
288 • The skin, hair and nails
extravasation and entrapment in the collagen and elastic fibres
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
a feature of dermatomyositis, especially on the eyelids.
Macular purpura may be the result of thrombocytopenia or
capillary fragility, but palpable purpura (often painful) usually
indicates vasculitis (Fig. 14.7A) and necessitates exclusion of
vasculitic inflammation in other organs. Purpura elicitable by
pinching the skin (‘pinch purpura’) may be indicative of AL
(light-chain) amyloidosis (Fig. 14.7B).
The vascular contribution to the colour of a rash can be pivotal
in diagnosis since erythematous and purpuric eruptions usually
have very different underlying causes. 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 remain within blood vessels;
non-blanchable redness (purpura) is the result of erythrocyte
Fig. 14.4 Necrobiosis lipoidica diabeticorum.
Fig. 14.5 Lichen planus. A Discrete flat-topped papules on the wrist.
B Wickham striae, visible on close inspection. C A white lacy network of
Fig. 14.6 Rash morphology. A Koebner response. B Pemphigoid.
The physical examination • 289
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
with a wooden orange stick (Fig. 14.8AB), the urtication that
develops when the pigmented lesions of urticaria pigmentosa
(a form of cutaneous mastocytosis) are rubbed (Darier’s sign),
the separation of epidermis on applying a shearing force in
pemphigus (Nikolsky’s sign), and the very earliest lesions of
lichen planus glinting in reflected light like stars in the night sky
Scratch marks (excoriations) indicate an itchy rash. In any
pruritic eruption it is prudent to look specifically for the burrows
of scabies (Fig. 14.9) on the hands and feet, as well as testing
for dermographism and examining for lymphadenopathy (p. 33),
as urticaria and lymphoma are also important causes of itch.
Fig. 14.7 Purpura. A Cutaneous vasculitis. B AL (light-chain) amyloidosis.
Fig. 14.8 Clinical signs in the diagnosis of skin disease. A Psoriasis
before rubbing the surface. B After surface rubbing. C Lichen planus
showing light reflection from small early lesions.
290 • The skin, hair and nails
Fig. 14.10 Lesion morphology. A Malignant
A B melanoma. B Seborrhoeic keratosis.
Lesions should be measured and described according to
their anatomical location, colour, symmetry, surface texture,
consistency, demarcation of margin, and whether they are
freely mobile or attached to underlying tissue (p. 32). Remember
to examine the regional lymph nodes. If a pigmented lesion
demonstrates a variable outline and colour variation, the possibility
of malignant melanoma must be considered (Fig. 14.10A). It
is reassuring to see hair growing out of pigmented lesions, as
this usually indicates a benign process such as a melanocytic
naevus. An irregularly roughened, jagged surface texture is
often indicative of sunlight-induced damage (actinic keratosis),
whereas the surface of a seborrhoeic keratosis (Fig. 14.10B) 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; 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
General physical examination should always include the hair
and nails. Is there excess hair, either in a masculine distribution
(hirsutism) or not (hypertrichosis), or hair loss (alopecia)? Hirsutism
may be a marker for hyperandrogenism, and 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 characteristic of
alopecia areata (Fig. 14.12), an autoimmune disorder that may
coexist with other autoimmune disorders. Diffuse, pronounced
hair shedding (telogen effluvium) may be a physiological response
to severe illness, major surgical operations or childbirth, and
may be accompanied by transverse grooves on the finger nails,
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 24 and in Box 3.4 and Fig. 3.7.
The physical examination • 291
Some rare diseases produce specific nail appearances,
such as the ‘ragged cuticles’ and abnormal capillary nail-bed
loops associated with dermatomyositis (Fig. 14.13AB), and the
progressive thickening and opacification of nails in yellow nail
Supplementary examination techniques
It is often necessary to complement naked-eye observation of the
skin with assisted examination techniques, such as 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. 14.14).
292 • The skin, hair and nails
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).
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.
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 overpigmented epidermis (making
conditions such as vitiligo and melasma easier to see); and it can
identify certain infections by inducing the causative organisms
to fluoresce (such as erythrasma, pityriasis versicolor and some
After clinical examination, specific investigative techniques may
be necessary in some cases to enable a precise diagnosis.
This involves a sample of skin being removed, under local
anaesthesia, and subjected to histological or immunohistochemical
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