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The power of making a correct diagnosis is the key to all success in the treatment of skin diseases; without this faculty, the physician can never be a thorough dermatologist, and therapeutics at once cease to hold their proper position, and become empirical.
LOUIS A DUHRING (1845–1913)
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Skin disorders are common. They account for 10.8% of all problems1 encountered in general practice, the most common being dermatitis/eczema, malignant skin neoplasms, solar keratoses, lacerations, warts and acne.
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This chapter focuses on the common dermatoses.
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Dermatitis is a nonspecific inflammatory response of the skin, presenting as an erythematous rash, that is usually itchy, and sometimes scaly.2 The terms dermatitis and eczema are often used interchangeably, with eczema referring to the process that causes dermatitis.
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Dermatitis can be divided into exogenous causes (allergic contact, primary irritant contact, photo-allergic and phototoxic) and endogenous, which implies all forms of dermatitis not directly related to external causative factors. Endogenous types are atopic, nummular (discoid), vesicular hand/foot (pompholyx), pityriasis alba, lichen simplex chronicus and seborrhoeic.
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Dermatitis can occur as the result of dry skin, which impairs the barrier function of the skin, making it more susceptible to irritation by soap and other contact irritants, the weather, temperature and non-specific triggers.
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The term ‘atopic’ refers to a hereditary background or tendency to develop one or more of a group of conditions, such as allergic rhinitis, asthma, eczema, skin sensitivities and urticaria. It is not synonymous with allergy.
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An estimated 10% of the population are atopics, with allergic rhinitis being the most common manifestation.3
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Features of classic atopic dermatitis:2,4
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itch
usually a family history of atopy
about 3% of infants are affected, signs appearing between 3 months and 2 years
often known trigger factors (see TABLE 121.1) are evident
consider environmental allergens (e.g. dust mite, grasses, pollen, animal dander) especially if concurrent allergic rhinitis and prominent facial or periorbital involvement (usually older than 2 years)
food allergies are rarely the main cause of the condition
lichenification may occur with chronic atopic dermatitis
flexures are usually involved (see FIG. 121.1)
dryness is usually a feature
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