|
|
 |
|||||
 |
|
||||
|
|
Residents were traditionally taught that the prevalence of atopic dermatitis in children was between 8% and 10%. The prevalence has since increased dramatically, peaking at approximately 20% to 25% in 5- to 10-year-old children. Results of a study on the frequency of atopic dermatitis in schoolchildren showed a prevalence of 17.2% in children 5 to 9 years old. In another study, a cohort of 8,530 children up to age 42 months showed a prevalence of 25% in children 6 to 18 months old and almost 20% in children 30 to 42 months. Furthermore, 80% to 90% of patients with atopic dermatitis are diagnosed by age 5.
The increased incidence of atopic dermatitis does not appear to be simply a result of increased interest and awareness by physicians. Reports suggest that the increase is a function of industrialization and development, although the exact cause is unknown. The increased incidence is important, however, because the health care system must allocate more resources to care for these patients.
The increase in prevalence of atopic dermatitis in children may have occurred too rapidly to be attributable to genetic factors. Industrialization could account for the increase, according to a recent study from Singapore. The prevalence of atopic dermatitis in highly industrialized Singapore was approximately 16% to 21.6%. In contrast, the prevalence in Malaysia, a country ethnically similar to Singapore but primarily rural, was approximately 3% to 5%. Other investigators hypothesize that environmental factors in developed nations, such as indoor pollution, contribute to the increase in atopic dermatitis.
|
Studies have also been performed to assess a possible relationship between the prevalence of atopic dermatitis and breast-feeding. In a recent European study of more than 8,000 infants exclusively breast-fed, 23.3% experienced atopic dermatitis during the first year of life. Results of the study show that exclusive breast-feeding did not influence the risk of atopic dermatitis during the first year of life. The study also showed no relationship to a smoking parent and an inverse relationship to the presence of a furry pet in the household, if the children were exposed to the furry pet in the first year of life. A study from New Zealand showed a 15.8% prevalence of atopic dermatitis in children at 3.5 years of age. In this study, breast-feeding duration was associated with an increased risk of atopic dermatitis. The data showed no association with socioeconomic status, maternal smoking, immunization, body mass index, or antibiotic exposure in the first year of life.
Allergies are sometimes thought to cause atopic dermatitis, although definitive data that demonstrate that food allergies cause atopic dermatitis are not available. Evidence in specific cases of environmental allergens such as dust mites exists, but a causal relationship between environmental allergies and atopic dermatitis has not been demonstrated. It is clear that people who are genetically predisposed to developing atopic disorders, probably because of exposure to allergens or irritants, may develop atopic dermatitis.
Also, new data are available on disruption of the skin barrier function. A study showed that a mutation in the filaggrin gene, a protein that helps form the skin barrier, could cause ichthyosis vulgaris. This gene mutation, which is present in approximately 10% of Europeans, also appears to be a predisposing factor for atopic dermatitis.
Determining proper treatment for patients depends on recognizing the disease. Clinical presentation typically changes with age. Patients also may present with acute, subacute, and/or chronic dermatitis. Furthermore, the condition is characterized by exacerbations and remissions. The patient’s skin is hyperirritable and “itchy.” If the patient does not scratch and parents do not report scratching, or if the clinician does not observe excoriations, then the patient is unlikely to have atopic dermatitis.
|
||||||
Factors that exacerbate atopic dermatitis include anxiety or stress; weather conditions such as temperature and humidity; irritants such as detergents, solvents, wool or other rough materials; perspiration; contact or inhaled antigens; and, less often, food.
Acute dermatitis, which is not necessarily atopic dermatitis, presents with swelling, blistering, redness, crusting, and occasionally secondary infection (Figure 1a). Chronic dermatitis presents with hyperpigmentation, thickening of the skin or lichenification, and scale that develop over weeks or months (Figure 1b).
Patterns indicating atopic dermatitis typically change with age. From birth through early infancy, only the diaper area is unaffected by the condition. Atopic dermatitis is not suspected in children who wear diapers and have diaper dermatitis. Atopic dermatitis should be considered in dermatitis that involves any other area and is itchy (Figure 2).
|
||||
Extensor surface and flexural area skin involvement is common in children with atopic dermatitis in preschool and early school-age years. Atopic dermatitis in children 2 to 10 years old may present with acute and chronic changes in the flexural crease of the arm, the flexural crease at the buttocks, and the dorsal flexural crease on the tops of the feet. Many patients also develop small staphylococcus abscesses under fingernails from scratching and autoinoculating the area and can present with blistering distal dactylitis.
Lesions may be restricted to the flexural creases in older children. Some lesions may go into remission, and some may be restricted to the hands and feet. Adolescents may present with dermatitis on the hands and feet as a late manifestation of atopic dermatitis. Depigmentation, or vitiligo, may also develop.
Some patients do not exhibit classic age-related patterns. Other clinical findings, although not specific for atopic dermatitis, raise the possibility of diagnosis. Prurigo nodularis for example may indicate atopic dermatitis (Figure 3a). Children who pick at the dermatitis create severe thickening of the skin and itching nodules. Other patients may present with hyperlinearity such as increased markings on the palms and the soles of the feet or with pigmentary changes.
Ichthyosis vulgaris may also be a marker for atopic dermatitis in children. It is important to recognize that although ichthyosis is distinct from atopic dermatitis, it may manifest along with atopic dermatitis. These patients present with large, coarse, noninflammatory adherence scaling, usually on the arms and legs but sometimes more widely disseminated. I do not recommend treating patients with ichthyosis with topical anti-inflammatory steroids but rather with a mild lubricant.
Children with keratosis pilaris (Figure 3b) may also be at risk for developing atopic dermatitis. Symptoms include retention of scale around follicular structures on the upper anterior thighs, the upper arms, and the lateral cheeks.
Nummular dermatitis, which presents with coin-shaped, acute dermatitic lesions, may indicate an acute manifestation of atopic dermatitis. Although nummular dermatitis can be a manifestation of other dermatides, atopic dermatitis should be considered in patients with other markers for atopic dermatitis.
Pityriasis alba, although another potential marker for atopic dermatitis, is not a definitive finding of atopic dermatitis. Patients with pityriasis alba may have subtle inflammatory atopic dermatitis that produces hypopigmentation, particularly in the summer when they do not tan evenly. These patients may have chronic low-grade contact dermatitis or seborrheic dermatitis.
Other clinical findings associated with atopic dermatitis include Dennie-Morgan folds, which are extra folds of skin around the eyes, similar to those seen in patients who itch and scratch due to environmental allergies. If these patients present with flexural disease, atopic dermatitis may be present.
Follicular or papular eczema is a disease in transition. Follicular structures are slightly raised from the skin surface. When rubbed and scratched, areas around follicular structures are first to become lichenified. Therefore, when a patient is healing and the large plaques are breaking up, distinct follicular papules may appear. When disease begins to flare, these distinct follicular papules are seen before the plaques develop.
Autoeczematization may also indicate atopic dermatitis. Autoeczematization is an immunologically mediated inflammatory dermatitic process that can be triggered by an acute localized dermatitis. Lymphocytes become activated, circulate, and produce widespread dermatitis.
Finally, some infants age 6 weeks or younger may have what I call “atopic seborrhea,” which is not symptomatic. Atopic dermatitis and seborrheic dermatitis can occur simultaneously in this age group. These young patients may be fussy, scratching, and rubbing their heads and necks against their parents and bedsheets. Although an antiseborrheic shampoo may alleviate the seborrheic component, the atopic component could worsen. If a physician evaluates a child with cradle cap who is itching, the physician should consider concomitant atopic dermatitis in this patient.
Pediatricians and dermatologists must acknowledge that the causes of atopic dermatitis and genetic markers are not known. Clinicians should consider the condition a genetic disorder with environmental triggers. By identifying the age-related patterns and associated clinical findings, clinicians will be able to diagnose atopic dermatitis and provide patients with proper treatment.
|
||||||
Selected References
- Borchers AT, Keen CL, Gershwin ME. Hope for the hygiene hypothesis: When the dirt hits the fan. J Asthma. 2005;42:225-247.
- Eigenmann PA, Sicherer SH. Borkowski TA, Cohen BA, Sampson HA. Prevalence of IgE-mediated food allergy among children with atopic dermatitis. Pediatrics. 1998;101:E8.
- Irvine AD, McLean WH. Breaking the (un)sound barrier: Filaggrin is a major gene for atopic dermatitis. J Invest Dermatol. 2006;126;1200-1202.
- Kidon MI, Chiang WC, Liew WK, et al. Sensitization to dust mites in children with allergic rhinitis in Singapore: Does it matter if you scratch while you sneeze? Clin Exp Allergy. 2005;35:434-440.
- Laughter D, Istvan JA, Tofte SJ, Hanifin JM. The prevalence of atopic dermatitis in Oregon schoolchildren. J Am Acad Dermatol. 2000;43:649-655.
- Ludvigsson JF, Mostrom M, Ludvigsson J, Duchen K. Exclusive breastfeeding and risk of atopic dermatitis in some 8300 infants. Pediatr Allergy Immunol. 2005;16:201-208.
- Purvis DJ, Thompson JM, Clark PM, et al. Risk factors for atopic dermatitis in New Zealand children at 3.5 years of age. Br J Dermatol. 2005;152:742-749.
- Tay YK, Kong KH, Khoo L, Goh CL, Giam YC. The prevalence and descriptive epidemiology of atopic dermatitis in Singapore school children. Br J Dermatol. 2002;146;101-106.
- Wadonda-Kabondo N, Sterne JA, Golding J, et al. A prospective study of the prevalence and incidence of atopic dermatitis in children aged 0-42 months. Br J Dermatol. 2003;149:1023-1028.
Bernard A. Cohen, MD, is associate professor of pediatrics and dermatology at Johns Hopkins University School of Medicine in Baltimore.
[Introduction]
[The epidemiology of atopic dermatitis in children: Incidence, causes and control]
[The treatment of atopic dermatitis in children: A review of therapeutic options]
[Clinical insight: Case management for children with atopic dermatitis]
[Panel Discussion]
