Clinical manifestations of atopic dermatitis
The term dermatitis, non-specific and generic, only indicates that the disease is characterized by inflammation of the epidermis and dermis, and is therefore not infectious.
Not all dermatitis can be diagnosed as atopic dermatitis or atopic eczema
In addition, in atopic dermatitis, the cutaneous manifestations are typical and vary according to the age of the person and are decisive in establishing the clinical diagnosis.
But above all, atopy must be present.
What is atopy?
Atopy is a biological condition and it is the intrinsic characteristic of the disease that differentiates it from all other forms of dermatitis such as allergic contact dermatitis or dermatitis of an irritative nature.
Therefore, only if this condition is present can a certain skin inflammation be diagnosed as atopic dermatitis.
The term atopy refers to a personal or family hypersensitivity of the skin and/or mucous membranes to common environmental stimuli that leads to increased production of IgE and the development of symptoms such as conjunctivitis or asthma, or skin manifestations such than eczema.
Three important elements emerge from the above definition:
- Familiarity: this is the presence of atopic diseases in relatives of the person with atopic dermatitis because a genetic predisposition is present. Studies have shown alterations of chromosomes 3, 5 and 11 and the presence of atopic dermatitis in 80% of homozygous twins, identical twins sharing the same DNA, and only in 30% of heterozygous twins. Furthermore, a defect in a specific protein of the epidermis, filaggrin, has recently been demonstrated, an alteration also present in ichthyosis vulgaris.
- Hypersensitivity of the skin or mucous membranes: various substances, chemical, physical, biological, are capable of triggering a series of so-called atopic diseases, such as bronchial asthma, rhinitis or conjunctivitis. Thus, within the same household, one person may suffer from bronchial asthma and another from atopic dermatitis. Apparently different diseases whose common denominator is atopy, which is clinically expressed in different ways in different individuals.
- Hyperproduction of IgE: increase in IgE antibodies in the serum as a biological defense response to various possible triggers and irritants or as a consequence of an allergy that the person with atopic dermatitis may have developed. I emphasize that atopic dermatitis is not an allergy but could develop it as shown below.
Clinical manifestations of atopic dermatitis
A person is born with atopic dermatitis, a defect that constitutes the outermost layer of the skin, the epidermis, where there is a defect in the skin barrier that defends us daily from external aggressions.
This barrier defect is due to a quantitative and qualitative alteration of certain lipid substances (cholesterol, essential fatty acids, ceramides) normally placed between the keratinocytes and to a filaggrin defect.
The outermost layer of the skin can be compared to the plaster of a wall which, only if intact, is able to preserve the bricks from atmospheric agents.
Similarly, it is only if the barrier function is intact that our skin is able to counter external aggressions, for example the chemical products of a detergent.
The damage to the barrier facilitates the penetration of irritating substances, capable of activating the inflammatory and immunological processes typical of atopic dermatitis, which, as mentioned, manifests itself differently in different age groups.
Infant: the initial manifestation is a localized yellowish desquamation on the scalp, called milky scab, which, when present, does not necessarily imply the diagnosis of atopic dermatitis because it can only be a distinct manifestation. Only medical history can raise suspicion of atopic dermatitis if there is a family history of atopy.
First two years: patches of eczema localized electively on the cheeks, forehead, chin with the perioral region spared. In addition to the face, the trunk and extensor surfaces of the limbs may also be affected. The plaques are well defined and erythematous in color, covered with scales and serous crusts. When the dermatitis is particularly extensive, lymphadenopathy, that is, an increase in the size of the lymph nodes, may be noted. For example, if dermatitis is present on the face, the submandibular or retroauricular lymph nodes may enlarge.
Childhood and adolescence: patches of dermatitis appear on the folds of the elbows, wrists, neck, back of the ears, knees and back of the hands. Given the site, cracks, sometimes painful, can often be observed.
Adult: The affected sites are similar to the previous ones but in this case the scrotum, the ankles and the neck can also be affected.
Itching, a ubiquitous symptom in atopic dermatitis
Itching is the ubiquitous symptom.
There is no atopic dermatitis without itching which, if particularly intense, incites the person to scratch, favoring the formation of scratching lesions but also the appearance of lichenification, a rough grayish thickening characterized by an accentuation of the physiological texture of the skin surface with a consequent loss of skin plasticity.
Moreover, it can be the cause of restlessness as it can interfere with a person’s sleep.
Bacterial infections are very common, but so are viral or fungal infections.
In the first case, Staphylococcus aureus can induce impetigo in patches of atopic dermatitis which become moist and exudative, covered with yellowish crusts.
Herpes simplex and varicelliform herpes are the most common causes of viral infections along with molluscum contagiosum.
Finally, with regard to fungal infections, P. ovale is responsible for the persistence of patches of atopic dermatitis on the upper third of the trunk in young women.
Evolution and triggering factors of atopic dermatitis
Recurrence is the salient feature of atopic dermatitis, which tends to improve in summer and then worsen in fall and winter, triggered by several factors
- aggressive and especially foaming detergents;
- irritating clothing made of synthetic fibers or wool;
- profuse sweating;
- infectious episodes;
- stressful emotional factors.
Most people with atopic dermatitis tend to improve after puberty while maintaining easily irritated skin.
However, between 5 and 50% of patients continue to suffer from atopic dermatitis in adulthood.
Treatment is based on the severity of the disease as assessed by the prescribing physician using certain scales that take into account the severity of the signs and/or symptoms of the disease.
Treatment for mild forms of atopic dermatitis is topical treatment, which involves the use of emollients to soothe dry skin, cortisone or calcineurin inhibitors during the inflammatory phase, and antibiotics only if there is infection.
Only in severe cases is systemic therapy indicated, including cortisone, cyclosporine, or dupilumab.
In addition to these, phototherapy is a valuable aid in the treatment of atopic dermatitis.
A working group of specialists, possibly European, has drawn up the 2019 guidelines for a critical and timely approach to atopic dermatitis.