The Dutch hypothesis (chronic non-specific lung disease) revisited.

In 1961 the hypothesis (later referred to as the Dutch Hypothesis (DH)) was put forward that asthma, chronic bronchitis and emphysema should be considered as different expressions of one disease entity, in which both endogenous (host) and exogenous (environmental) factors play a role in the pathogenesis. A hereditary predisposition to develop allergy and bronchial hyperreactivity were considered to be important denominators of disease susceptibility. Complications and complicating diseases would also contribute to the ultimate phenotype of the patient. In the present paper we discuss the relevance of this hypothesis in 1990. Until now it has not been refuted; circumstantial evidence in its favour has accumulated, but formal proof is still lacking. Further research should pay more attention to the genetic aspects of the disease. Arguments are presented against the use of the terms asthma, chronic bronchitis, and emphysema as indicators of disease entities, and in favour of the use of an umbrella-term, e.g. chronic non-specific lung disease (CNSLD), provided that, in addition, every patient is characterized using so-called defining criteria.