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What is wheezing?

Wheezing is defined as a continuous, mainly expiratory, high-frequency musical sound that is heard mainly during expiration and is usually associated with partial obstruction in some part of the respiratory tract. It is one of the most common symptoms in preschool children. Almost 30% of children have at least one episode of wheezing before their third birthday and 50% of children report at least one episode of wheezing by the age of 6. The most common cause of wheezing episodes in young children is upper and lower respiratory tract infections.

What is bronchial asthma?

Asthma is one of the most common childhood diseases. The basic characteristics of asthma are chronic inflammation of the bronchi, varying degrees of their obstruction and bronchial hyperreactivity to various stimuli. Bronchial hyperreactivity is the tendency of the tracheobronchial tree to react, causing bronchospasm, to various non-specific stimuli (e.g. inhalation of cold air such as during physical exercise, infectious agents).

The most characteristic symptoms of asthma are wheezing, shortness of breath, chest tightness and cough. As asthma is a heterogeneous disease, its symptomatology varies from patient to patient and fluctuates over time. The etiology of asthma is multifactorial since many environmental factors in combination with genetic predisposition have been implicated in its occurrence.

Is wheezing in preschool age synonymous with the term Childhood Asthma?

Are recurrent episodes of wheezing in preschool age (Preschool Wheeze) and bronchial asthma two different diseases with similar symptomatology or a single entity with age-dependent symptomatology? This is a controversial issue.

Indeed, wheezing is a typical symptom of asthma, but it can also occur in children without asthma, especially in early preschool age.The diagnosis of asthma in early childhood cannot be easily established since the ability to demonstrate the existence of chronic airway inflammation and to measure airway obstruction is limited.

According to the Global Initiative for Asthma Guidelines (GINA), recurrent episodes of wheezing, coughing and dyspnea, especially when they occur during the night, as well as the response to treatment (e.g. with bronchodilators) are some indicative signs for the diagnosis of asthma in children aged 5 years or younger. It is very important, especially in cases of severe symptoms without a clear response to standard asthma treatment, to exclude other conditions that mimic asthma symptoms (such as cystic fibrosis or anatomical abnormalities of the bronchial tree).

Will a child with recurrent wheezing episodes in preschool continue to have the same symptoms after the age of six?

What we know so far is that two-thirds of children with one or more wheezing episodes in preschool outgrow their symptoms by the age of six, while the remaining one-third will continue to have the same symptoms in school age. These symptoms point to a diagnosis of asthma. At school age, it is possible to use diagnostic tests to investigate possible asthma, such as spirometry.

To date, it is particularly difficult to predict which children will continue to have wheezing episodes after preschool age, but some important risk factors have been found. Allergic sensitization, exposure to cigarette smoke, and viral respiratory infections such as rhinovirus infections in early preschool age have been identified as important risk factors for bronchial asthma.

Of course, rhinovirus infection in early childhood does not cause wheezing or asthma in all children, but there is literature that suggests that in children with a genetic predisposition to developing asthma, the risk of the disease increases significantly after rhinovirus infection in early childhood. It is known that hereditary predisposition contributes to the development of asthma, and genetic variants have been found that are specifically associated with childhood asthma.

However, a small percentage of the heritability of asthma is due to the genetic variants known so far (e.g. in the 17q21 locus). Asthma is a multifactorial disease caused by a combination of genetic and environmental factors. Therefore, genetic testing for asthma has not, at least to date, been implemented in daily clinical practice.

Treatment and prevention

Several therapeutic approaches have been proposed therapeutic treatments based on different classifications (phenotypes) of preschool wheezing. Most patients with mild intermittent wheezing in preschool age can be treated with inhaled bronchodilators when necessary.

Most cases of severe or frequent wheezing episodes can be effectively treated with inhaled corticosteroids or leukotriene modifiers, either as monotherapy or in combination[MOU1]. Since not all children respond to the recommended treatment in the same way, determining the wheezing phenotype and individualizing the treatment is important. There is no clear literature data indicating a specific drug treatment for the prevention of bronchial asthma.

However, it is worth mentioning that exposure to cigarette smoke in childhood significantly increases the risk of developing asthma, while breastfeeding, attendance at preschools, and exposure to a rural environment have a protective role.