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Atopic and Contact Dermatitis

Mark Boguniewicz, Luz Fonacier, Donald Y.M. Leung

Atopic dermatitis (AD) and contact dermatitis (CD) are common age, other diseases need to be considered in adults with new-onset
1,2
inflammatory skin diseases. The complex pathophysiology of dermatitis, especially in those without a history of childhood
AD involves both underlying skin barrier abnormalities and eczema, asthma, or allergic rhinitis (see Table 44.1, Differential
immune dysregulation. Its course is augmented by environmental Diagnosis). Although in some children, AD may progress to
influences, including stress, allergen exposure, and microbial milder forms of eczema, only in approximately one-third will
infection. Patients with AD experiencing a relapsing course benefit the disease be eliminated altogether. Severity and atopic sensitiza-
from a proactive approach with skin emollients and antiinflam- tion are major determinants of prognosis. A US registry of patients
matory therapy (e.g., intermittent use of a topical steroid or with mild-moderate AD showed that it was not until age 20
calcineurin inhibitor). The identification of new immune pathways years that 50% had experienced at least one 6-month period
associated with AD has resulted in the development of novel free of symptoms and treatments. 5
biologicals targeting patients with refractory AD.
CD is a skin disorder caused by contact with an exogenous Clinical Features
substance that elicits an allergic and/or irritant response. Allergic AD has no pathognomonic skin lesions or unique laboratory
contact dermatitis (ACD) accounts for 20%, whereas irritant parameters; the diagnosis is, therefore, based on the presence of
contact dermatitis (ICD) accounts for 80% of all cases of CD. major and associated clinical features (Table 44.2). The principal
ACD is a delayed-type, T cell–mediated immune response features include pruritus, a chronically relapsing course, typical
consisting of an afferent limb and an efferent limb. Irritants morphology and distribution of skin lesions, and a history of
cause direct activation of the innate immune system through atopic disease. Patients usually have dry xerotic skin, and those
hyperproduction of cytokines and chemokines. The management with mutations of the gene encoding the epidermal barrier protein
of ACD includes identification of the allergen, avoidance, filaggrin (FLG) typically have prominent scaling and hyperlinear
pharmacological intervention, and prevention. This chapter palms. Acute AD is characterized by pruritic, erythematous papules
reviews the clinical and mechanistic aspects of both AD and CD. associated with excoriations, vesiculations, and serous exudate.
Subacute AD is characterized by erythematous, excoriated, scaling
CLINICAL ASPECTS OF ATOPIC DERMATITIS papules, whereas chronic AD is characterized by lichenification
and fibrotic papules. During infancy, AD involves primarily the
Epidemiology face, scalp, and the extensor aspects of the extremities; the diaper
Prevalence of AD has been documented in up to 24% of children, region is typically spared, although some infants manifest the
with no apparent difference seen between urban and rural districts flexural involvement typical of older patients (Fig. 44.1).
or between the two sexes. Children from families with atopy
have a significantly higher risk of developing AD. Data from an Complicating Features
international study (ISAAC Phase 3) showed that prevalence of Ocular Problems
current eczema in children varies widely among countries, ranging Atopic keratoconjunctivitis is bilateral, with intense pruritus,
from 0.9% to 22.5%, and in adolescents, the prevalence ranges burning, tearing, and copious mucoid discharge. It is frequently
3
from 0.2% to 24.6%. These data point to the significance of associated with eyelid dermatitis and chronic blepharitis and
AD being a global health problem in both developed and develop- may result in visual impairment from corneal scarring. Patients
ing countries and suggest that the ultimate presentation of an may also develop keratoconus from persistent rubbing of the
atopic disease may depend on a complex interaction between eyes or anterior subcapsular cataracts.
environmental exposures and end-organ response in genetically
predisposed individuals. Prevalence of adult eczema from a Hand Dermatitis
nationally representative sample found that the 1-year prevalence Patients with AD may have a nonspecific irritant hand dermatitis
of eczema was 10.2% and that the 1-year prevalence of eczema aggravated by repeated wetting, especially in an occupational
with asthma and/or hay fever was 3.2%. 4 setting.
Natural History Infections
AD typically manifests in early childhood, with onset in the first Patients with AD have an increased susceptibility to infection
2
year occurring in >50% of patients and before 5 years of age in or colonization with a variety of organisms. Staphylococcus aureus
approximately 90% of patients. Although AD can present at any can be cultured from the skin of the majority of patients with
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