The „Wheezy baby syndrome“ is a typical, although poorly defined, disease entity occurring frequently mainly during acute viral respiratory illnesses in infants and toddlers. Some wheezy children will develop true bronchial asthma, while others will „grow out“ of the problem. There are still no clearly defined risk factors reliably predicting the development of bronchial asthma in these children. In this prospective study, twenty seven young children (19 boys, 8 girls, aged 3 - 35 months) with severe episodes of wheezing had a detailed clinical and laboratory examinations (IgG, IgA, IgM, IgG subclasses 1 - 4, total IgE, specific IgE and ECP) during the acute episode and were subsequently followed-up for 7 - 20 months. At the end of the follow-up period the laboratory tests were repeated. A mild degree of humoral immunodeficiency was found in 16 children (59%) at enrolment and in 8 children (36%) at the end of the study. Of the 27 patients with wheezing, 12 children (49.4%) had increased concentrations of total IgE. At the end of the study, children were assigned to one of two groups: 1) 14 children with asthma, 2) 13 children without signs of asthma. There were no significant differences between asthmatic and non-asthmatic children in the levels of IgG, IgA, IgM, IgE, but serum ECP levels were significantly elevated in asthmatics (p < 0.01) at the time of enrolment. Young children with severe episodes of wheezing requiring emergency medical care are at high risk of developing bronchial asthma. The clinical evaluation and close follow-up still remain the most important factors for diagnosing asthma. Routine laboratory tests aiming at the detection of humoral immunodeficiency and atopy should be supplemented by the evaluation of serum concentration of ECP even during the first severe episode of wheezing.

        Key words: bronchial asthma, wheezing, young children, IgE antibodies, eosinophilic cationic protein (ECP)