An Atlas of Atopic Eczema

Lionel Fry

• Publisher: CRC Press
• Year: 2003
• ISBN:
  9781135400972
• Edition: 1
• Topic: Medicina
• Subtopic: Teoría, práctica y referencia médicas

Atopic eczema is the most common and persistent dermatological condition seen in general practice. Over the last few years, advances have been made in the genetics of atopy in general, newer treatments have been introduced for topical use, and new concepts suggested in the etiology. Thus, a new text on atopic eczema is both timely and useful. Writt

1 DEFINITIONS

DERMATITIS VERSUS ECZEMA

The words ‘dermatitis’ and ‘eczema’ are used synonymously in the dermatological literature. Dermatitis derives from the Greek word derma, meaning skin. However, the word ‘dermis’ is now applied to the structure of the skin below the basement membrane, whilst that above is called the epidermis. Thus, it could be argued that dermatitis, strictly speaking, refers to the dermis and not to the whole skin. Eczema is derived from the Greek word ekzein, meaning ‘to boil over’, and is a purely descriptive term. Which term is more accurate is debatable. In this book, the term eczema is preferred, but the choice is arbitrary.

ATOPIC

The word ‘atopic’ is derived from the Greek word topos, meaning place, and was applied in the sense ‘out of place’. The term was coined to denote an abnormal hypersensitive response to an environmental allergen and the word ‘atopen’ is now synonymous with allergen. Two allergists, Coco and Cooke, first used the term ‘atopic’ in 1923¹, and the term ‘atopic dermatitis’ originated in 1933. However, the condition that is now described by this term is considerably older and can be recognized in early Chinese and Roman writings.

At present, there is no universal agreement about the definition of atopic eczema. Some believe that immunoglobulin E (IgE)-specific antibodies to environmental antigens are part of the disease and the term atopic eczema should not be used if IgE allergen-specific antibodies are not present².If the clinical features suggest atopic eczema but no IgE antibodies are present, the term ‘atopiform’ eczema has been proposed². Others believe that atopic eczema defines a clinical state with characteristic features. The clinical criteria postulated by Hanifin and Rajka³ are still the most appropriate. They give four major features, of which at least three must be present. These are:

1. (1) Pruritus; (2) Lichenification; (3) Chronic relapsing course; (4) Personal and/or family history of asthma, allergic rhinitis/conjunctivitis and a family history of atopic eczema.

In addition, three minor features should be present. These include dryness of the skin, ichthyosis vulgaris, keratosis pilaris, immediate skin test (type 1) reactivity, elevated IgE level, tendency to cutaneous infection with Staphylococcus aureus and herpes simplex, increased incidence of hand and foot and nipple eczema, cheilitis, recurrent conjunctivitis, Dennie-Morgan infraorbital fold, anterior subcapsular cataracts, orbital darkening, facial pallor/erythema, pityriasis alba, anterior neck folds, itch when sweating, intolerance to wool, perifollicular accentuation, food intolerance, course often affected by emotional/ environmental factors, and white dermographism.

More simple criteria were proposed by Williams and colleagues ⁴. These are: a history of an itchy skin rash in the last 12 months plus three or more of the following:

1. (1) History of flexural involvement; (2) History of asthma and/or hay fever; (3) History of generalized dry skin; (4) Onset of rash before the age of 2 years (not applicable if the patient is under 4 years); (5) Visible flexural involvement.

These criteria are not as precise as those of Hanifin and Rajka and may not be applicable to young children and infants.

Figure 1 Atopic disease may occur singularly or in combination. A, asthma; E, eczema; H, hay fever

It should be remembered that 100% uniformity does not exist in clinical medicine and there are always exceptions to the clinical criteria as proposed both by Hanifin and Rajka, and by Williams and colleagues.

A causative role for IgE antibodies in atopic eczema is still disputed and other pathogenetic mechanisms have been implicated. Until these have been fully elucidated, it would be prudent to maintain the clinical criteria for diagnosing atopic eczema.

IgE antibodies are found in 70–80% of patients with atopic eczema. The terms ‘intrinsic’ and ‘extrinsic’ have been used to imply that evidence exists for an external allergen based on IgE antibodies. The term ‘extrinsic atopic eczema’ is used when antibodies are present and ‘intrinsic’ when the antibodies are absent. How useful this subdivision is at the clinical level is debatable at present but, with greater understanding of the pathogenesis of atopic eczema in the future, this subdivision may then be relevant.

Atopic eczema is strongly associated with asthma, rhinitis and conjunctivitis, due to external allergens. However, as with eczema, the demonstration that the disease is due to an external allergen is not always proven. Asthma is also divided into intrinsic and extrinsic subdivisions. Collectively, eczema, asthma and hay fever are sometimes referred to as the atopic syndrome. However, it is important to stress that the three manifestations of the atopic syndrome may occur singularly and not necessarily all together (Figure 1).

INFANTILE ECZEMA

Atopic eczema is sometimes still referred to as infantile or flexural eczema because of its early age of onset and the characteristic sites of the disease. However, the term ‘atopic eczema’ is to be preferred because other types of eczema may occur in infancy and may affect flexures. In addition, there are prognostic and genetic implications associated with atopic eczema that are different from the other patterns of eczema seen in childhood.

2 EPIDEMIOLOGY

PLACE OF DOMICILE

Epidemiological studies on atopic eczema have been carried out, particularly in European countries. However, the accuracy of these studies is dependent on the definitions of atopic eczema that were used, and the fact that many are based on questionnaires rather than on an interview and examination by a dermatologist. There are also variations in the questions posed and the age of the groups studied. Thus, some studies have only taken the incidence of eczema at a particular point in time and others have included past history.

Using point prevalence (i.e. presence of eczema at that particular point), the incidence of the disease in European countries ranges from 5.3 to 26%, with a mean of 13% in the groups aged 3–12 years ⁵. In one of the largest studies conducted worldwide, questionnaires were completed on 458 623 individuals, aged 13–14 years. The incidence of atopic eczema ranged from more than 15% in some northern European countries to less than 5% in China, central Asia and eastern European countries⁶. There was a suggestion that the line of latitude had an effect in that the closer to the equator the country was, the lower the incidence of the disease. However, it is interesting to note that, when individuals migrate from areas of low incidence to those of a higher incidence, the incidence of atopic eczema rises in the immigrant population and is often higher than in the local population. Thus, environmental factors are of considerable importance in determining the incidence of atopic eczema. In addition, an increased incidence of the disease appears to be associated with a move from a rural/agricultural society to an industrial one. It has been shown, in a study in Ibadan in Nigeria, that the incidence of atopic eczema increased with the progressive industrialization of the area and an associated change in lifestyle. Thus, change in lifestyle may be more important than the change in the latitude of the country of residence.

INCIDENCE OF ATOPIC ECZEMA RELATED TO AGE

It is generally agreed that the incidence of atopic eczema decreases as children become older and the incidence is considerably less in adult life. As already mentioned, the incidence of atopic eczema in northern European countries is relatively high in children, particularly in urban areas. Several studies give an ncidence of 10–15% and most of these studies are for the age group 3–11 years⁷. The studies do not distinguish between the incidences at age 3 and age 11. A few studies have examined the incidences in the 0–4–year age group, where they ranged from approximately 10 to 15%. Studies in teenagers have shown considerably lower incidences in the same countries and these range from approximately 2 to 3%. The frequency in adults is even lower; over the age of 25, the incidence has been reported to be less than 0.2%⁸. Thus, to inform parents that children usually grow out of their eczema is correct.

INCREASING INCIDENCE OF ATOPIC ECZEMA

It has been thought that the incidence of atopic eczema has increased over the last 50 years. However, the figures supporting this observation may not be reliable because of the criteria and techniques used to arrive at these results. The criteria for diagnosing atopic eczema and the concept of the disease have changed over time. Many of the figures are based on parents’ recall of the rash in their children and no objective examinations were carried out in most of the studies. If these limitations are accepted, then the figures do show an increasing incidence of atopic eczema in children. In children up to 7 years, the incidence for those born before 1960 ranged from 1.4 to 3.1%, with a mean of 2.2%. For those born between 1960 and 1970, the frequency ranged from 3.8 to 8.8%, with a mean of 6.7%, and, for those born after 1970, the range was 8.9–20.4%, with a mean of 12.0%⁹. This increased incidence of atopic eczema is supported by twin studies from Denmark. The cumulative incidence rate for twins born between 1960 and 1964 was 3% and for those born between 1975 and 1979 it rose to 12% ¹⁰.

This increase in the incidence of atopic eczema is similar to the reported increase in asthma seen over the last 40 years.

3 NATURAL HISTORY

Although there have been several studies on the natural history of atopic eczema, there are a number of variable factors in these studies that may influence their reliability. First, the definition of the disease was not consistent. Second, the length of time of follow-up was variable. Third, some of the studies were hospital-based while others were community-based. It is likely that community-based studies will show milder disease than a hospital-based population and the severity of the disease may influence the natural history.

It is generally agreed that atopic eczema usually commences in childhood. In nearly 50% of patients, the age of onset is before 6 months, with 60% before 1 year and 70% before 5 years ¹¹. It is also accepted that atopic eczema will go into remission in early life. In a general practice setting over a 40-year study period, it was found that 50% of cases had cleared by the age of 5 years and 90% by the age of 10 (J. Fry, personal communication). In a British cohort study, 65% had cleared by age 11 and 74% by age 16¹². In a hospital-based study over a 5–20-year period, the clearance rates ranged from 84 to 92%¹³. Thus, there is general agreement that atopic eczema is primarily a disease of childhood, with the majority clearing before or during adolescence. However, in a smaller proportion, atopic eczema may present for the first time in adult life, and in some individuals, whose eczema began in infancy, the disease will persist into adult life. The factors that determine these variations are yet to be elucidated but; similar to the basic causes of the disease, they are likely to be partly constitutional and partly environmental. It is also well known that, in patients whose atopic eczema has cleared, there is always a risk that it may recur because of inherent factors. Occupations and hobbies in later life, involving exposure to chemicals that may damage the stratum corneum, may induce eczematous reactions, either for the first time or as a recurrence in those with a past history of atopic eczema.

Various factors have been implicated in a poor prognosis. These include severe disease at onset; extensor or inverse pattern of eczema on the knees and elbows in children; family history of atopic eczema, particularly if both parents are affected; concomitant asthma; and subjects who were not breast-fed. However, these are also studies disputing these factors as poor prognostic indicators.

The risk of developing asthma and hay fever in children with atopic eczema has been reported in a number of studies¹⁴. The main criticisms of these studies are that the period of study was too short or that the subjects were chosen from a hospital-b...

Table of contents

• COVER PAGE
• TITLE PAGE
• COPYRIGHT PAGE
• 1: DEFINITIONS
• 2: EPIDEMIOLOGY
• 3: NATURAL HISTORY
• 4: GENETICS
• 5: PATHOGENESIS
• 6: ETIOLOGY
• 7: CLINICAL FEATURES
• 8: DIFFERENTIAL DIAGNOSIS
• 9: MANAGEMENT
• REFERENCES