Clinical forms of asthma. Exogenous asthma

From an immunological point of view , two subgroups of patients with asthma can be distinguished: 1) patients with an indication of external or exogenous factors provoking seizures, and 2) patients in whom such provocative agents are not detected (cryptogenic or endogenous asthma) [Rackermann, 1947]. 

Exogenous asthma caused by a specific external allergen can, in turn, be subdivided depending on whether the patient has atopy (i.e., severe skin reactions of type I to a standard set of common allergens) or no atopy. In patients with atopic exogenous asthma, symptoms usually appear at an early age.

In 80% of asthma patients with positive skin tests observed by us, symptoms appeared before the age of 30. In many of these cases, spontaneous remission occurs and, according to estimates, perhaps in 9 out of 10 children with atopic exogenous asthma, attacks are significantly weakened or disappear when the children reach older adolescents [Rackermann, Edwards, 1952; Dees, 1957; Buffum, 1963; Barr, Logan, 1964; Williams, McNicol, 1969; Leveque, Therond, 1972].  

The exact number of patients in whom the symptoms persist, according to these authors, is different, especially at different ages at which the disease began, and different severity of symptoms. The prognosis is usually worse in cases of early development of asthma and its severe course [Williams, McNicol, 1969].  

Natural remission in patients with childhood asthma may be consistent with Soothill’s theory of a transient immune defect, due to which mainly IgE is formed in the early years of life, but the tendency to its formation gradually decreases in the future.

The weakening of atopic reactivity with age is also proved by data on the relationship between the age at which asthma symptoms appear and the frequency of skin reactions to common allergens [Hendrick et al., 1975]. In patients with late-onset asthma, usually positive reactions to injection tests are less common.  

Another subgroup of exogenous asthma – non-atopic exogenous asthma – includes patients whose symptoms are associated with a specific agent with which they often have contact during work, and symptoms often appear after prolonged and high doses of contact.  

In these patients, skin tests for a standard set of common allergens are negative, but an immediate, late or double reaction to a specific sensitizing agent may be observed. They can detect specific antibodies IgE, IgG. However, their presence in each given case mainly depends on whether it was possible to prepare the corresponding well-purified antigens. As already mentioned, in some cases, the mechanism of asthma can be non-immunological.  

In patients with exogenous non-atopic asthma, symptoms usually appear at an older age. For reasons that will be explained below, after sensitization has already begun, the asthmatic reaction, like in people with atopy, can be caused by a wide variety of non-immunological stimuli, for example: infection, physical exertion, emotions or some factors associated with the circadian rhythm .  

event_note October 18, 2019

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