Atopic Dermatitis

Atopic dermatitis is a chronic, relapsing inflammatory skin disease characterized by eczematous lesions accompanied by itching. It is a heterogeneous condition encompassing various subtypes that arise from complex interactions among genetic, immunologic, and environmental factors. Diagnosis is not made through a single objective test but rather through a comprehensive assessment of detailed medical history, physical examination findings, and laboratory results. Clinical features, examination findings, and test results can vary depending on ethnicity, country, region, and age.

1. Classification according to age

 1-1. Infantile type (under 2 years of age)

• This form typically begins around 2–3 months of age with dry, red, and scaly eczematous lesions on the cheeks. The lesions gradually spread to other areas of the face, neck, wrists, abdomen, and extensor surfaces of the limbs. In later stages, flexural areas may also become involved. In infants who wear diapers, it is common for the diaper area to be spared, as they are unable to scratch this region. Most cases tend to improve by ages 3 to 5, but some may progress to the childhood or adult type, or develop other atopic diseases.

1-2. Childhood type (2–12 years of age)

• Lesions primarily affect flexural areas of the body, such as the antecubital and popliteal fossae, wrists, ankles, and neck. The eczema tends to present as dry papules that often coalesce into plaques and, with chronicity, develop lichenification.

1-3. Adult type (after 12 years of age)

• This type typically begins around puberty, although the exact cause is unclear. Hormonal changes and psychological stress have been suggested as contributing factors. The distribution pattern is similar to the childhood type, with frequent involvement of flexural areas and the development of widespread lichenified lesions.

2. Classification according to atopic status

 2-1. Extrinsic type

• The extrinsic type, accounting for approximately 60–80% of cases, is characterized by elevated total serum IgE, positive specific IgE tests, peripheral eosinophilia, a family history of atopy, coexisting atopic diseases, and a high frequency of filaggrin gene mutations. 

2-2. Intrinsic type

• The intrinsic type, which accounts for 20–40% of cases, presents with normal IgE levels, negative allergy test results, and no association with other atopic diseases. It is more commonly observed in females, tends to have a later onset, and is associated with relatively preserved skin barrier function.

In the acute phase of atopic dermatitis, skin lesions typically appear as erythematous papules and plaques. Intense itching leads to scratching, which may result in erythematous, weepy dermatitis with oozing. As the disease progresses into a subacute or chronic phase, the moist lesions tend to become dry, and the skin shows lichenification due to thickening. These various skin findings may appear in combination, and the condition tends to become chronic through repeated episodes of acute inflammation.

Commonly observed clinical features include the following:

• Scalp scaling
• Auricular fissures
• Subgluteal eczema