Atopic dermatitis is a chronic, recurrent, inflammatory, pruritic dermatological disease whose pathogenesis involves both inflammatory factors and abnormal skin barrier function. It is currently believed that atopic dermatitis occurs in a significant genetic background. It is associated with the progress of industrialization, environmental factors, dietary factors, indoor and outdoor air pollution, fetal growth, and early infections. Atopic dermatitis usually develops before the age of 5 years, and may also develop in adults, but less frequently. Patients often feel extremely itchy skin, and after scratching, the affected skin becomes red, swollen, cracked, oozes clear fluid, and finally hardens and flakes. Some children improve or recover with age, but their skin remains dry and easily irritated, and some children continue to suffer from atopic dermatitis even as they grow into adults.
What is “atopic”?
The key to an accurate definition and scope of atopic dermatitis and to distinguishing atopic dermatitis from eczema and other skin conditions is an understanding of “atopic. The term “atopic” means
(i) a familial predisposition to develop asthma, allergic rhinitis, or eczema.
(ii) Allergy to allergic proteins.
(iii) High serum IgE values.
④ an increase in eosinophils in the blood.
A typical atopic dermatitis must have ① – ④ along with clinical manifestations of eczema.
Clinical classification of atopic dermatitis
1. Exogenous atopic dermatitis
There is a personal or family history of respiratory allergy (e.g. asthma, allergic rhinitis, chronic cough) with elevated levels of total IgE in the blood, and atopic allergens can be detected. Seen in 70% of patients with atopic dermatitis.
2. Endogenous atopic dermatitis
The patient has no family history of respiratory allergy, and the total IgE level in the blood is normal. and no specific allergens can be detected. Early onset with dry dermatitis. Seen in 30% of patients with atopic dermatitis.
Triggering factors of atopic dermatitis
1, the relationship with allergic reactions: respiratory allergic reactions are often associated with atopic dermatitis. The most common allergens are dust mites, pollen, animal dander and molds.
2, and food allergens relationship: mainly seen in infants and children suffering from moderate to severe atopic dermatitis. Milk, eggs, peanuts, soybeans and wheat are the most common allergens. Consumption of eggs is often associated with exacerbation of atopic dermatitis. Reactions to peanuts, fish, nuts, and shellfish have a tendency to persist.
3. Reactions to microorganisms: Microorganisms, especially Staphylococcus aureus, colonize more than 90% of the atopic dermatitis lesions. Patients with atopic dermatitis are also prone to viral infections and superficial fungal infections.
Clinical staging and signs of atopic dermatitis
Atopic dermatitis is divided into 3 clinical stages, namely, infancy, childhood, and adolescence or early adulthood, depending on age, site of onset, and morphologic changes in the lesions. These stages may cross over each other or may be separated by the self-healing of the disease at one stage.
Infantile stage (birth – 2 years): In the infantile stage, it occurs mostly in infants after 40 days of life, and a few may develop within the first month of life. The manifestations are acute and subacute eczema, with lesions on the scalp, face and extensor side of the limbs, and chapping, oozing and crusting at the eardrum; the diaper area is generally not involved; the affected child is consciously and intensely itchy. At about 18 months of age, the characteristic flexural (elbow and popliteal fossa) involvement begins to appear and mossy changes occur. By 2 years of age, about 80% of infants with atopic dermatitis will be largely cured, with the remainder entering childhood.
Childhood (3 – 11 years): Childhood atopic dermatitis can be a continuation of the infantile period or a new onset in childhood. It is characterized by a mossy appearance and presents as an eczematous and itchy rash. The flexural involvement is more pronounced and can spread to the neck, wrist flexure and inguinal area, and in those with generalized lesions the extensor calf, hands, perioral and periocular areas can also be involved. It is called ‘four bends of wind’ in Chinese medicine.
Adolescence or early adulthood (12 – 20 years old): lesions tend to occur on the face, neck, flexors and upper trunk, and the main symptoms are pruritus, mossy changes, itchy rash, scratches and crusting, with dry skin and mossy changes remaining the most prominent features. There is often a typical central pale area on the face. Most patients have spontaneous regression of the lesions after the age of 20 years; a few severe cases may persist into old age.
Signs that aid in the diagnosis of atopic dermatitis
Atopic dermatitis can be accompanied by a range of characteristic skin changes, including dry skin, auricular fissures, ichthyosis, palmaris, follicular keratosis, infraorbital folds, orbital bursal dark halo, peri-hair elevation, nonspecific hand and foot dermatitis, white pityriasis, anterior cervical folds, papillary eczema, recurrent conjunctivitis, and white scratchy sign.
Difference and connection between atopic dermatitis and eczema
Although current textbooks and reference books treat atopic dermatitis and eczema separately, the general international academic view is that there is no such thing as eczema of unknown origin, and that eczema is only a temporary diagnostic term, and as research progresses, eczema with an identified cause is diagnosed as the corresponding dermatitis.
The early manifestations of atopic dermatitis are very similar to those of common eczema in infants. For example, red papules the size of a pinhead appear on the face, and there are also symmetrical erythema and scaling, and in severe cases, redness, small blisters, vesicles and exudation, often accompanied by very pronounced itching, but the two still have their own characteristics.
One, atopic dermatitis is generally more symptomatic compared to common eczema. The latter rash is more limited, occurring only in a certain part of the child’s body, such as the cheeks, back of the hand, etc.; while the former rash is more extensive, often affecting the scalp, ear, and in severe cases, the trunk, limbs, including the back of the hands and feet can be involved, and with age, the typical hypertrophic, mossy rash gradually appears in the neck, elbow fossa, popliteal fossa.
Second, atopic dermatitis is more prone to recurrence compared to common eczema. Children with atopic dermatitis have a mild to severe disease that often lasts >3 months.
Third, children with atopic dermatitis can have abnormally dry, rough skin, and 60% – 70% of children have a family history of asthma, allergic rhinitis, or atopic dermatitis.
Fourth, children with atopic dermatitis may have pallor, dark circles under the eyes, ichthyosis, diffuse dandruff, and labyrinthitis.
Many of the current eczemas such as ear eczema, breast eczema and hand eczema are among the manifestations of atopic dermatitis at different times and in different locations.