Diseases - Atopic Dermatitis - Part 1

 

What is atopic dermatitis?

Atopic dermatitis is a chronic (long-lasting) disease that affects the skin. The word "dermatitis" means inflammation of the skin. "Atopic" refers to diseases that are hereditary, tend to run in families, and often occur together. These diseases include asthma, hay fever, and atopic dermatitis. In atopic dermatitis, the skin becomes extremely itchy and inflamed, causing redness, swelling, cracking, weeping, crusting, and scaling.

Atopic dermatitis most often affects infants and young children, but it can continue into adulthood or first show up later in life. In most cases, there are periods of time when the disease is worse, called exacerbations or flares, which are followed by periods when the skin improves or clears up entirely, called remissions. Many children with atopic dermatitis enter into a permanent remission of the disease when they get older, although their skin often remains dry and easily irritated. Environmental factors can activate symptoms of atopic dermatitis at any time in the lives of individuals who have inherited the atopic disease trait.

What is the difference between atopic dermatitis and eczema?

Eczema is a general term for many types of skin inflammation (dermatitis). Atopic dermatitis is the most common of the many types of eczema. Several other forms have very similar symptoms. The diverse types of eczema are listed and briefly described below.

Types of Eczema

• Atopic dermatitis: a chronic skin disease characterized by itchy, inflamed skin
  
• Contact eczema: a localized reaction that includes redness, itching, and burning where the skin has come into contact with an allergen (an allergy-causing substance) or with an irritant such as an acid, a cleaning agent, or other chemical
  
• Allergic contact eczema: a red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy or certain preservatives in creams and lotions
  
• Seborrheic eczema: a form of skin inflammation of unknown cause that presents as yellowish, oily, scaly patches of skin on the scalp, face, and occasionally other parts of the body
  
• Nummular eczema: coin-shaped patches of irritated skin-most commonly on the arms, back, buttocks, and lower legs-that may be crusted, scaling, and extremely itchy
  
• Neurodermatitis: scaly patches of skin on the head, lower legs, wrists, or forearms caused by a localized itch (such as an insect bite) that becomes intensely irritated when scratched
  
• Stasis dermatitis: a skin irritation on the lower legs, generally related to circulatory problems
  
• Dyshidrotic eczema: irritation of the skin on the palms of hands and soles of the feet characterized by clear, deep blisters that itch and burn

How common is atopic dermatitis?

Atopic dermatitis is very common. It affects males and females equally and accounts for 10 to 20 % of all referrals to dermatologists (doctors who specialize in the care and treatment of skin diseases). Atopic dermatitis occurs most often in infants and children and its onset decreases substantially with age. Scientists estimate that 65 percent of patients develop symptoms in the first year of life, and 90 percent develop symptoms before the age of 5. Onset after age 30 is less common and often occurs after exposure of the skin to harsh conditions. People who live in urban areas and in climates with low humidity seem to be at an increased risk for developing atopic dermatitis.

About 10% of all infants and young children experience symptoms of the disease. Roughly 60 percent of these infants continue to have one or more symptoms of atopic dermatitis even after they reach adulthood. This means that more than 15 million people in the United States have symptoms of the disease.

What causes atopic dermatitis?

The cause of atopic dermatitis is not known, but the disease seems to result from a combination of genetic (hereditary) and environmental factors. Evidence suggests that the disease is associated with other so-called atopic disorders such as hay fever and asthma, which many people with atopic dermatitis also have. In addition, many children who outgrow the symptoms of atopic dermatitis go on to develop hay fever or asthma. Although one disorder does not cause another, they may be related, thereby giving researchers clues to understanding atopic dermatitis.

In the past, it was thought that atopic dermatitis was caused by an emotional disorder. We now know that emotional factors such as stress can exacerbate, but do not cause the condition.

Is atopic dermatitis contagious?

No. Atopic dermatitis is definitely not contagious; it cannot be passed from one person to another. There is no cause for concern in being around someone with even an active case of atopic dermatitis.

What are the symptoms of atopic dermatitis?

Symptoms vary from person to person. The most common symptoms are dry, itchy skin, cracks behind the ears, and rashes on the cheeks, arms, and legs. The itchy feeling is an important factor in atopic dermatitis, because scratching and rubbing in response to itching worsen the skin inflammation that is characteristic of this disease. People with atopic dermatitis seem to be more sensitive to itching and feel the need to scratch longer in response. They develop what is referred to as the "itch-scratch" cycle. The extreme itchiness of the skin causes the person to scratch, which in turn worsens the itch, and so on. Itching is particularly a problem during sleep, when conscious control of scratching decreases and the absence of other outside stimuli makes the itchiness more noticeable.

How atopic dermatitis affects the skin can be changed by patterns of scratching and resulting skin infections. Some people with the disease develop red, scaling skin where the immune system in the skin becomes very activated. Others develop thick and leathery skin as a result of constant scratching and rubbing. This condition is called lichenification. Still others develop papules, or small raised bumps, on their skin. When the papules are scratched, they may open (excoriations) and become crusty and infected. The box below lists common skin features of the disease. These conditions can also be found in people without atopic dermatitis or with other types of skin disorders.

Can atopic dermatitis affect the face?

Yes. Atopic dermatitis may affect the skin around the eyes, the eyelids, and the eyebrows and lashes. Scratching and rubbing the eye area can cause the skin to change in appearance. Some people with atopic dermatitis develop an extra fold of skin under their eyes, called an atopic pleat or Dennie-Morgan fold. Other people may have hyperpigmented eyelids, meaning that the skin on their eyelids darkens from the inflammation or hay fever (allergic shiners). Patchy eyebrows and eyelashes may also result from scratching or rubbing.

Is the sufferer's skin type important?

Yes. Differences in the skin of people with atopic dermatitis may contribute to the symptoms of the disease. The epidermis, which is the outermost layer of skin, is divided into two parts: the inner part, which contains moist, living cells; and the outer part, which consists of dry, flattened, dead cells. Under normal conditions, the outer layer of skin acts as a barrier, keeping the rest of the skin from drying out and protecting other layers of skin from damage caused by irritants and infections. When this barrier is damaged or is naturally thin, irritants act more intensely on the skin.

The skin of a person with atopic dermatitis loses too much moisture from the epidermal layer. This allows the skin to become very dry, which reduces its protective abilities. In addition, the skin is very susceptible to recurring disorders, such as staphylococcal and streptococcal bacterial skin infections, warts, herpes simplex, and molluscum contagiosum (which is caused by a virus).

Skin Features of Atopic Dermatitis

• Lichenification: thick, leathery skin resulting from constant scratching and rubbing
  
• Papules: small raised bumps that may open when scratched, becoming crusty and infected
  
• Ichthyosis: dry, rectangular scales on the skin
  
• Keratosis pilaris: small, rough bumps, generally on the face, upper arms, and thighs
  
• Hyperlinear palms: increased number of skin creases on the palms
  
• Urticaria: hives (red, raised bumps), often after exposure to an allergen, at the beginning of flares, or after exercise or a hot bath
  
• Cheilitis: inflammation of the skin on and around the lips
  
• Atopic pleat (Dennie-Morgan fold): an extra fold of skin that develops under the eye
  
• Hyperpigmented eyelids: eyelids that have become darker in color from inflammation or hay fever

What are the stages of atopic dermatitis?

Atopic dermatitis affects each child differently, both in terms of onset and severity of symptoms. In infants, atopic dermatitis typically begins around 6 to 12 weeks of age. It may first appear around the cheeks and chin as a patchy facial rash, which can progress to red, scaling, oozing skin. The skin may become infected. Once the infant becomes more mobile and begins crawling, exposed areas such as the knees and elbows may also be affected. An infant with atopic dermatitis may be restless and irritable because of the itching and discomfort. Many infants improve by 18 months of age, although they remain at greater than normal risk for dry skin or hand eczema later in life.

In childhood, the rash tends to occur behind the knees and inside the elbows, on the sides of the neck, and on the wrists, ankles, and hands. Often, the rash begins with papules that become hard and scaly when scratched. The skin around the lips may be inflamed, and constant licking of the area may lead to small, painful cracks. Severe cases of atopic dermatitis may affect growth, and the child may be shorter than average.

The disease may go into remission. The length of a remission varies, and it may last months or even years. In some children, the disease gets better for a long time only to come back at the onset of puberty when hormones, stress, and the use of irritating skin care products or cosmetics may cause the condition to flare.

Although a number of people who developed atopic dermatitis as children also experience symptoms as adults, it is unusual (but possible) for the disease to show up first in adulthood. The pattern in adults is similar to that seen in children; that is, the disease may be widespread or limited. In some adults, only the hands or feet may be affected and become dry, itchy, red, and cracked. Sleep patterns and work performance may be affected, and long-term use of medications to treat the condition may cause complications. Adults with atopic dermatitis also have a predisposition toward irritant contact dermatitis, especially if they are in occupations involving frequent hand wetting, hand washing, or exposure to chemicals. Some people develop a rash around their nipples. These localized symptoms are difficult to treat, and people often do not tell their doctor because of modesty or embarrassment. Adults may also develop cataracts that are difficult to detect because they cause no symptoms. Therefore, the doctor may recommend regular eye exams.

How is atopic dermatitis diagnosed?

Currently, there is no single test that says unequivocally "this is atopic dermatitis" and there is no single symptom or feature that can be used to identify the disease. Each patient experiences a unique combination of symptoms, and the symptoms and severity of the disease may vary over time. The doctor bases the diagnosis on the individual's symptoms and may need to see the patient several times to make an accurate diagnosis. It is important for the doctor to rule out other diseases and conditions that might cause skin irritation. In some cases, the family doctor or pediatrician may refer the patient to a dermatologist or allergist (allergy specialist) for further evaluation.

A valuable diagnostic tool is a thorough medical history, which provides important clues as to the possible causes of the patient's ailment. The doctor may ask about all of the following: a family history of allergic disease; whether the patient also has diseases such as hay fever or asthma; exposure to irritants; sleep disturbances; any foods that seem to be related to skin flares; previous treatments for skin-related symptoms; use of steroids; and the effects of symptoms on schoolwork, career, or social life. Sometimes, it is necessary to do a biopsy of the skin or patch testing to determine if the skin's immune system overreacts to certain chemicals or preservatives in skin creams. A preliminary diagnosis of atopic dermatitis can be made if the patient has three or more characteristics from each of two categories: major features and minor features. Some of these characteristics are listed in the box below.

Skin scratch/prick tests (which involve scratching or pricking the skin with a needle that contains a small amount of a suspected allergen) and blood tests for airborne allergens generally are not as useful in diagnosing atopic dermatitis as a medical history and careful observation of symptoms. However, they may occasionally help the doctor rule out or confirm a specific allergen that might be considered important in the diagnosis. Negative results on skin tests are reliable and may help rule out the possibility that certain substances are causing skin inflammation in the patient. However, positive skin scratch/prick test results are difficult to interpret in people with atopic dermatitis and are often inaccurate. In some cases, where the type of dermatitis is unclear, blood tests to check the level of eosinophils (a type of white blood cell) or IgE (an antibody whose levels are often high in atopic dermatitis) are helpful.

... to be continued