Diseases due to commensal overgrowth Sometimes, ‘normal’ commensals can result in disease. Among the most common are the following: ● Pitted keratolysis . Overgrowth of resident microorganisms that digest keratin; occurs with occluding footwear and sweaty feet ( Fig. 28.1 ). Malodorous pitted erosions and punched out, discoloured areas result. Better hygiene, topical neomycin or soaks with 0.01% aqueous potassium permanganate or 3% aqueous formaldehyde usually…

The skin is a barrier to infection but, if its defences are penetrated or broken down, numerous microorganisms can cause disease ( Table 27.1 ). Table 27.1 Bacterial diseases of the skin Organism Infection Commensals Erythrasma, pitted keratolysis, trichomycosis axillaris Staphylococci Impetigo, ecthyma, folliculitis, secondary infection Streptococci Erysipelas, cellulitis, impetigo, ecthyma, necrotizing fasciitis Gram-negative Secondary infection, folliculitis, cellulitis Mycobacterial Tuberculosis (lupus vulgaris, warty tuberculosis, scrofuloderma), fish…

Photodermatoses—idiopathic Polymorphic light eruption Polymorphic light eruption is often incorrectly referred to as ‘prickly heat’ (a different condition) and is characterized by pruritic papules, plaques and sometimes vesicles that last for days in light-exposed areas. Clinical presentation This is the commonest photodermatosis, and women are affected twice as frequently as men. Pruritic urticated papules, plaques and vesicles develop on light-exposed skin usually about 24 hours after…

Definition Erythroderma or generalized exfoliative dermatitis defines any inflammatory dermatosis that involves all or nearly all the skin surface (sometimes stated as more than 90%). It is a secondary process and represents the generalized spread of a dermatosis or systemic disease throughout the skin. Pathology The duration and severity of the inflammatory process play a greater part in determining the histology than the underlying cause. In…

Papulosquamous eruptions are raised, scaly and marginated, and include psoriasis, lichen planus and other conditions listed in Box 24.1 . Eczema is not included as it does not usually have a sharp edge. These eruptions are not related aetiologically. Several are characterized by fine scaling and have the prefix ‘pityriasis’, which means ‘bran-like scale’. Box 24.1 Papulosquamous eruptions Chronic superficial dermatitis Drug eruption (p. 106) Lichen…

Lichen planus and other disorders with a lichenoid appearance of shiny flat-topped papules are presented here. Lichen planus Lichen planus is a relatively common pruritic papular dermatosis involving the flexor surfaces, mucous membrane and genitalia. The cause is unknown, but an immune pathogenesis for lichen planus is suspected as T cells infiltrate the skin, immunoglobulin M is found at the dermoepidermal junction, a lichenoid eruption is…

The other main types of dermatitis are seborrhoeic, hand, pompholyx, discoid, venous, and asteatotic eczema. Seborrhoeic dermatitis Seborrhoeic dermatitis is a scaly eruption, usually affecting the scalp and eyebrows. Other patterns are recognized. The condition is usually less itchy than atopic eczema, but sometimes clinical distinction of these entities is difficult. Treatment is with mild topical corticosteroids and anti-yeast therapy ( Chapter 33 ). Hand dermatitis…

Definition Atopic eczema is predominantly a disease of childhood that gives rise to poorly demarcated chronic pruritic papular inflammation of the skin. Uncontrollable scratching is prominent. Most cases improve with age, although approximately 50% of children retain evidence of the condition into adult life. ‘Atopy’ defines those with an inherited tendency to develop asthma, allergic rhinitis, conjunctivitis or atopic eczema and is present in 15%–25% of…

Definition Allergic contact dermatitis is an eczema precipitated by an exogenous agent, often a chemical, which is recognized by the immune system as an antigen and results in T-cell-mediated inflammation. Often, irritant and endogenous factors are also involved in the clinical picture. Aetiopathogenesis Individual predisposition to allergic contact dermatitis varies. Similar exposures to chemicals in cosmetics, medicinal products or environmental allergens give rise to allergic reactivity…

Definition Eczema is a non-infective inflammatory skin condition that shows itching, redness, papulation and scaling. Eczema represents a reaction pattern to a variety of stimuli, some of which are recognized but many of which are unknown. Eczema and dermatitis mean the same thing and may be used interchangeably. Classification The eczemas represent a wide spectrum of conditions with varying prevalence and pathogenesis ( Table 19.1 ),…

Research has confirmed psoriasis to be an immune-mediated inflammatory disease, with associated genes involved in immune regulation ( Fig. 18.1 ). These recent discoveries have allowed the pharmaceutical industry to specifically design biologic drugs that work in psoriasis and in other diseases where there is improved comprehension of the pathomechanisms. Biologics block specific inflammatory mediators or cells (see Chapter 61 ). Other systemic drugs are assumed…

Planning treatment The non-infectious nature of psoriasis, its relapsing nature and the likely need for long-term therapy should be explained. A sympathetic approach is helpful, and patients often obtain support from the self-help group the Psoriasis Association. Treatment is tailored to the patient’s particular requirements, taking into account the type and extent of the disease, and the age and social background ( Table 17.1 ). NICE…

Definition Psoriasis is a chronic, non-infectious, inflammatory dermatosis characterized by well-demarcated erythematous plaques topped by silvery scales ( Fig. 16.1 ). Epidemiology Psoriasis affects 1.5%–3% of the population in Europe and North America, but is less common in Africa, China and Japan. The sex incidence is equal. The condition may start at any age, even in the elderly. The two peaks of onset are the second…

The stress of having skin disease The potentially harsh psychological effects of chronic skin disease tend to be underestimated. Up to 30% of skin outpatients suffer ‘psychological distress’ from their condition. This is understandable in the teenager with acne, or in someone who has extensive psoriasis or eczema. In both, the individual’s devalued body image may be out of proportion to the objective severity of his…

Skin disease is very common. About 10% of a GP’s workload and 6% of hospital outpatient referrals can be accounted for by skin problems. Skin disease is also economically significant; it is a major occupational cause of loss of time from work and the third most common industrial disease (p. 160). In any discussion of epidemiology, it is important first to define the terms used: ●…

Medical treatments for skin disease are increasingly focussed on systemic therapy, especially in secondary care. Biologic drugs are being developed to target specific pathways in the pathogenetic mechanisms of several skin diseases. Biologics are discussed in Chapter 61 . When to select systemic therapy Systemic treatments are used when topical treatment is ineffective, or for serious skin diseases and infections when a topical approach would be…

The treatment of skin disease includes topical, systemic, intralesional, radiation and surgical modalities. Specific treatments are detailed below. First is an overview of dermatological therapies. Topical therapy Topical treatment has the advantage of direct delivery and reduced systemic toxicity. It consists of a vehicle or base, which often contains an active ingredient ( Table 12.1 ). Table 12.1 An overview of topical medicaments Drug Indications Pharmacology…

The practice of close visual examination of skin lesions with a handheld magnifying glass and a light has been employed by dermatologists for many years. Dermoscopy (syn. dermatoscopy) was developed in the 1990s as a tool to reduce the reflectance of light from the skin surface and allow the user to gain visual information from deeper within the skin structures than is possible with traditional lighting.…

Dermatologists make use of several diagnostic and therapeutic procedures in their everyday clinical practice. Diagnostic procedures The ability to diagnose a skin disease is improved by the use of better methods of observing lesions and by appropriate use of samples for laboratory investigation. Patch tests and prick tests are described on pages 48 and 164. Dermoscopy, the taking of samples for fungal culture and microscopy, the…

The skin needs to be examined in good, preferably natural, light. The whole of the skin should be examined, ideally. This is essential for atypical or widespread eruptions ( Fig. 9.1 ). Looking at the whole skin often reveals diagnostic lesions that the patient is unaware of or may think unimportant. In the elderly, thorough skin examination often allows the early detection of unexpected but treatable…