What is asthma?

Abstract

While almost every paediatrician would agree that asthma is a very common condition in childhood, often underdiagnosed despite being a major cause of absence from school,' it has never been satisfactorily defined. True, there have been a number of more or less satisfactory attempts by august bodies such as the Ciba Guest Symposium2 and the Americah Thoracic Society,3 and one of the most lucid attempts to explain the definition of asthma was that of Professor J G Scadding.4 He made the point that the disease should be characterised by its functional effect: 'Asthma is a disease characterised by wide variations over short periods of time in resistance to flow in intrapulmonary airways'. Professor Scadding went on to point out that the definition can be amplified by comments on causative mechanisms where known. With typical clarity he also tackled the difficult question as to what constitutes 'wide variations' by suggesting that this means changes that are symptomatically and therapeutically important. This being so, what is the problem in defining asthma and why the need for this annotation? Physicians treating adult patients have long been troubled by the fact that chronic airflow obstruction can be due to chronic bronchitis, emphysema, asthma, or any combination of these conditions, and that it is often very difficult to separate the components. Many patients with these types of chronic obstructive lung disease have symptomatic and therapeutic variations in their airflow obstruction without ever reverting to normal or near normal lung function. To make matters worse, adults with asthma not infrequently smoke or reside in polluted areas, and add an irreVersible component to their disease. Finally, there are the occupational asthmas that can occur in anyone without any special predisposition to the disease5 and resolve after removal from the offending environment. For all these reasons and others, those treating adult patients can rarely agree on what constitutes asthma. We paediatricians often feel rather smug about asthma and tell our colleagues that we cannot see what all the fuss is about since the diagnosis is perfectly straightforward in children. But is it? If we accept Professor Scadding's definition4 as a good starting point and also that the adult type of chronic obstructive lung disease probably never occurs in childhood,σ ' what paediatric conditions could be confused with asthma and in what ways can asthma seem to be something else?