Pruritus

Pruritus simply means itching. It may be either generalised or localised. Scratch marks are usually present. Localised pruritus is usually caused by a dermatological condition such as dermatitis or eczema. Generalised pruritus may be caused by primary skin disease, systemic disease or psychogenic factors.

To determine the cause of the pruritus it is essential to examine the skin in detail (Table 15.4). Excoriations are caused by scratching, regardless of the underlying cause. Specific features of cutaneous diseases such as dermatitis, scabies (Figure 15.6) or the blisters of dermatitis herpetiformis should be looked for.

TABLE 15.4 Primary skin disorders causing pruritus

Figure 15.6 Scabies

Scattered fine papules with severe itching. Finger web involvement is common.

When primary skin diseases have been excluded, a detailed history and examination should be undertaken to consider the various systemic diseases listed in Table 15.5.

TABLE 15.5 Systemic conditions causing pruritus

Erythrosquamous eruptions

Erythrosquamous eruptions are made up of lesions that are red and scaly. They may be well demarcated or have diffuse borders. They may be itchy or asymptomatic.

When one is attempting to establish a diagnosis of an erythrosquamous eruption, the history is very important. First ask about the time course of the eruption, about a family history of similar skin diseases and whether or not there is a family history of atopy.

The presence or absence of itching and the distribution of the lesions (often on the extensor surfaces of the limbs) also give clues about the diagnosis.

Asymptomatic lesions on the palms and soles are suggestive of secondary syphilis, whereas itchy lesions in the same location would be more suggestive of lichen planus (Figures 15.7 and 15.8). Lichen planus is occasionally associated with primary biliary cirrhosis and other liver diseases, chronic graft-versus-host disease and drugs (e.g. gold, penicillamine). Scattered lesions of recent origin on the trunk would be more suggestive of pityriasis rosea (Figure 15.9), whereas more widespread, diffuse and intensely itchy lesions would be more suggestive of nummular eczema (Figure 15.10) (Table 15.6).

Figure 15.7 Lichen planus

With polygonal flat-topped violaceous lesions.

Figure 15.8 Lichen planus

With development of lesions in an area of trauma—the ‘Koebner’ phenomenon.

Figure 15.9 Pityriasis rosea

With scattered scaly oval lesions on the trunk and a larger ‘herald’ patch.

Figure 15.10 Nummular eczema

Typical scattered coin-like lesions of indolent dermatitis.

TABLE 15.6 Causes of erythrosquamous eruptions

Scaly lesions with a well-demarcated edge over the extensor surfaces are usually due to psoriasis (Figures 15.11 and 15.12).

Figure 15.11 Psoriasis

Typical bright red, scaly plaque with silvery scale over a joint.

Figure 15.12 Acute widespread pustular psoriasis

Often the eruption is bright red with bizarre patterns and pustules predominantly at the margins.

Blistering eruptions

There are a number of different diseases which will present with either vesicles or blisters (Table 15.7). Dermatitis can present as a blistering eruption, particularly acute contact dermatitis (Figure 15.13). See Questions box 15.2.

TABLE 15.7 Causes of blistering eruptions

Figure 15.13 Allergic contact dermatitis

From over-the-counter topical medication rubbed over congested sinuses.

Clinical features of bullous eruptions

Viral blisters such as those of herpes simplex virus infection (Figure 15.14) have a distinctive morphology (grouped vesicles on an erythematous background).

Figure 15.14 Primary herpes simplex virus infection in an adult

Shows typical widespread distribution around the mouth.

Bullous pemphigoid is a rare disease usually affecting older patients. Blisters are widespread, have a thick roof and tend not to rupture easily.

Pemphigus vulgaris is much more severe. It has thin-roofed blisters that readily rupture and form crusts. The affected superficial skin can be moved over the deeper layer (Nikolsky’s^c sign). Oral ulcers are common.

Dermatitis herpetiformis is characterised by a very itchy widespread vesicular or bullous eruption.

Porphyria cutanea tarda is characterised by clear or haemorrhagic tense blisters on the hands and other sun-exposed areas, hyperpigmentation and increased facial hair; many patients have hepatitis C and alcohol can induce symptoms (due to decreased uroporphyrinogen decarboxylase).

Erythroderma

Erythroderma is best thought of as the end-stage of numerous skin conditions (Table 15.8). The erythrodermic patient has involvement of nearly all the skin with an erythematous inflammatory process, often with exfoliation. There is usually associated oedema and loss of muscle mass. This represents that most unusual occurrence, a dermatological emergency.

TABLE 15.8 Causes of erythroderma

An attempt should be made to determine the underlying cause of the erythroderma, and this is best done based on history and examination. Specific treatment can then be directed at the underlying cause. Some patients with erythroderma will develop profound metabolic changes (including hypoalbuminaemia and extrarenal water loss), and these patients require constant supervision and monitoring until they have recovered from the acute phase of their illness.

The most common cause is eczema, which is usually of the atopic variety. These patients often have an intense pruritus. Some of them will develop a chronic unremitting erythroderma.

Pustular and crusted lesions

The clinical appearance of a pustular lesion results from accumulation of neutrophils. Such collections usually indicate an infective process; however, sterile pustules may form as part of a number of skin diseases due to the release of chemotactic factors following an immunological reaction.

A crust is a yellowish crystalline material that is found on the skin; it is made up of desiccated serum.

It is essential to determine whether or not a pustular lesion (or a group of pustular lesions) represents a primarily infectious process or an inflammatory dermatological condition. For example, pustular lesions on the hands and feet may either be due to tinea infection or be a primary pustular psoriasis or palmoplantar pustulosis (Table 15.9). See Questions box 15.3.

TABLE 15.9 Causes of pustular and crusted lesions

Dermal plaques

Plaques are localised thickenings of the skin which are usually caused by changes in the dermis or subcutaneous fat. These may be due to chronic inflammatory processes or scarring sclerotic processes (Table 15.10).

TABLE 15.10 Causes of dermal plaques

The pattern of involvement of the plaques, the age of the patient and other clinical features should enable a diagnosis to be established.

In Sweet’s syndrome there are painful red plaques and a high fever (acute febrile neutrophilic dermatosis); 10% have leukaemia.

Erythema nodosum

This is the best known of the group of diseases classified as nodular vasculitis. The lesions of erythema nodosum are usually found below the knee in the pretibial area and are erythematous, palpable and tender (Figure 6.36, page 191). There may be an associated fever (Table 15.11). Sarcoidosis is a common cause, but the skin changes in sarcoid can mimic almost any skin disease (except vesicles).

TABLE 15.11 Causes of erythema nodosum

Erythema multiforme

This is a distinctive inflammatory reaction of skin and mucosa. It is not a systemic disease. Characteristic discrete target lesions occur, particularly on the distal extremities (Figure 15.15). The periphery of these lesions is red, whereas the centre becomes bluish or even purpuric. The lesions can become bullous, and severe cases of this syndrome involve widespread desquamation of the mucosal surfaces (the Stevens-Johnson^d syndrome). In many cases the condition is precipitated by clinical or subclinical herpes simplex virus infection. Other causes include Mycoplasma pneumoniae, histoplasmosis, malignancy, sarcoidosis and drugs (including those that can cause toxic epidermal necrolysis). Sometimes no underlying cause of the erythema multiforme will be established.

Figure 15.15 Erythema multiforme

Shows classic iris or target lesions, secondary to herpes simplex virus infection of the lips.

Toxic epidermal necrolysis, on the other hand, is a systemic condition and usually secondary to a drug reaction. It results in a peeling of large skin areas. The major causes include penicillin, sulfonamides, phenytoin and non-steroidal anti-inflammatory drugs.

Hyperpigmentation

The presence of hyperpigmentation can be a clue to underlying systemic disease (Table 15.12).

TABLE 15.12 Causes of diffuse hyperpigmentation

ACTH = adrenocorticotrophic hormone.

Flushing and sweating

Flushing of the skin may sometimes be observed, especially on the face, by the examiner. Some of the causes of this phenomenon are presented in Table 15.13.

TABLE 15.13 Causes of facial flushing

Excessive sweating (hyperhidrosis) can occur with thyrotoxicosis, phaeochromocytoma, acromegaly, hypoglycaemia, autonomic dysfunction, stress, fever and menopause.

Skin tumours

Skin tumours are very common and are usually benign (Table 15.14).⁴ Most malignant skin tumours can be cured if they are detected early and treated appropriately (Table 15.15).

TABLE 15.14 Benign skin tumours

TABLE 15.15 Malignant skin tumours

^* John Templeton Bowen (1857–1941), Boston dermatologist.

Skin cancer often occurs in those predisposed individuals (with the fair skin of Celtic or Northern European origin) who undergo chronic exposure to ultraviolet light.

Skin cancers may present as flat scaly lesions or as raised scaly or smooth lesions. They may be large or small and they may eventually ulcerate. All non-healing ulcers should be considered to be skin cancer, until proven otherwise.

The earliest lesions are actinic (solar) keratoses, which are pink macules or papules surmounted by adherent scale (Figure 15.16). Basal cell carcinoma is characteristically a translucent papule with a depressed centre and a rolled border with ectatic capillaries (Figure 15.17). Squamous cell carcinoma is typically an opaque papule or plaque which is often eroded or scaly (Figure 15.18).

Figure 15.16 Actinic keratosis, slightly eroded and scaly

Higher on the forehead additional granular keratosis could be easily palpated.

Figure 15.17 Pigmented basal cell carcinoma

With pearly quality and depressed centre, in a patient with sun-damaged skin.

Figure 15.18 Squamous cell carcinoma

Malignant melanomas are usually deeply pigmented lesions that are enlarging and have an irregular notched border (Figure 15.19). There is often variation of pigment within the lesion. Malignant melanoma is likely if the lesion is Asymmetrical, has an irregular Border, has an irregular Colour and is large (Diameter >6 mm) and may be Elevated, referred to as the ABCDE checklist.^5,6 Patients with numerous large and unusual pigmented naevi (dysplastic naevus syndrome) are at an increased risk of developing malignant melanoma.

Figure 15.19 Superficial spreading melanoma, still confined to the upper dermis

The dermatological examination in internal medicine: a suggested method

(Figure 15.22)

Figure 15.22 Sites of some important skin lesions of the limbs, face and trunk SLE = systemic lupus erythematosus.

Even if the patient shows the examiner only a small single area of abnormality, proceed to examine all the skin.

After obtaining good lighting conditions and asking the patient to disrobe, begin by looking at the nails and hands. Paronychia is an infection of the skin surrounding the nails. Other changes to note include pitting (psoriasis, fungal infections) and onycholysis (e.g. thyrotoxicosis, psoriasis). Dark staining under the nail may indicate a subungual melanoma. Linear splinter haemorrhages (e.g. vasculitis) or telangiectasiae (e.g. systemic lupus erythematosus) may be seen in the nail bed.

A purplish discoloration in streaks over the knuckles may indicate dermatomyositis. Also look at the backs of the hands and forearms for the characteristic blisters of porphyria, which occur on the exposed skin. Papules and scratch marks on the backs of the hands, between the fingers and around the wrists may indicate scabies. Viral warts are common on the hands.

Look at the palms for Dupuytren’s contracture, pigmented flat junctional moles (which have a high risk of becoming malignant) and xanthomata in the palmar creases.

Next look at the forearms, where lichen planus may occur on the flexor surfaces (characterised by small shiny, purple-coloured papules) and psoriasis may be present on the extensor surfaces. Palpable purpura—raised bruising that indicates bleeding into the skin—may be seen on the arms, and indicates vasculitis. Acanthosis nigricans can occur in the axillae.

Inspect the patient’s hair and scalp. Decide whether or not the hair is dry and whether the distribution is normal. Alopecia may indicate male pattern baldness, recent severe illness, hypothyroidism or thyrotoxicosis. Patches of alopecia occur in the disease alopecia areata. Short broken-off hairs occur typically in systemic lupus erythematosus. In psoriasis there are silvery scales, which may be seen on the skin of the scalp. Metastatic deposits may rarely be felt as firm nodules within the skin of the scalp. Sebaceous cysts are common. The unfortunate examiner may find nits sticking to the head hairs.

Move down now to the eyebrows and look for scaling and greasiness, which are found in seborrhoeic dermatitis. A purplish erythema occurs around the eyelids in dermatomyositis. Xanthelasmata are seen near the eyelid.

Look at the face for rosacea, which causes bright erythema of the nose, cheeks, forehead and chin, and occasionally pustules and rhinophyma (disfiguring swelling of the nose). Acne causes papules, pustules and scars involving the face, neck and upper trunk. The butterfly rash of systemic lupus erythematosus occurs across the cheeks but is rare. Spider naevi may be present. Ulcerating lesions on the face may include basal cell carcinoma, squamous cell carcinoma or rarely tuberculosis (lupus vulgaris).

Benign tumours of the face include keratoacanthoma (a volcano-like lesion from a sebaceous gland) and congenital haemangiomas.

Look for the blisters of herpes zoster, which may occur strictly in the distribution of one of the divisions of the trigeminal nerve.

Inspect the neck, which is prone to many of the lesions that occur on the face. Rarely, the redundant loose skin of pseudoxanthoma elasticum will be seen around the neck.

Go on to inspect the trunk, where any of the childhood exanthems produce their characteristic rashes. Look for spider naevi. Campbell de Morgan spots are commonly found on the abdomen (and chest), as are flat, greasy, yellow-coloured seborrhoeic warts. Erythema marginatum (rheumatic fever) occurs on the chest and abdomen. Herpes zoster may be seen overlying any of the dermatome distributions.

Metastases from internal malignancies may rarely occur anywhere on the skin. Neurofibromas are soft flesh-coloured tumours; when associated with more than five ‘café-au-lait’ spots (brownish, irregular lesions), they suggest neurofibromatosis (von Recklinghausen’s disease). Pigmented moles are seen on the trunk and evidence of malignancy must be looked for with these. The patient’s buttocks and sacrum must be examined for bedsores, and the abdomen and thighs may have areas of fat atrophy or hypertrophy from insulin injections.

Go to the legs, where erythema nodosum or erythema multiforme may be seen on the shins. Necrobiosis lipoidica diabeticorum affects the skin over the tibia in diabetics. Pretibial myxoedema also occurs over the shins. Look for ulcers on either side of the lower part of the leg. Livedo reticularis is a net-like, red reticular rash that occurs in vasculitis, the anti-phospholipid syndrome and with atheroembolism.

Inspect the feet for the characteristic lesion of Reiter’s disease called keratoderma blennorrhagica, where crusted lesions spread across the sole because of the fusion of vesicles and pustules. Look at the foot for signs of ischaemia, associated with wasting of the skin and skin appendages. Trophic ulcers may be seen in patients with peripheral neuropathy (e.g. diabetes mellitus). Always separate the toes to look for melanomas.