medwireNews: Airway smooth muscle (ASM) is increased in preschool children with severe wheeze who subsequently develop asthma, results from a UK study show.
However, the researchers found no significant differences in other pathologic characteristics of established asthma between preschool wheezers who did and did not develop asthma in later childhood.
"We consider our data to indicate that future studies exploring the mechanisms underlying the persistence of preschool wheeze and its progression to asthma should focus on ASM," Sejal Saglani (Imperial College London) and colleagues comment in the Journal of Allergy and Clinical Immunology.
The findings come from a study of 51 children from whom endobronchial biopsy samples were taken at preschool age (6-58 months) and who were followed up at school age (6-11 years). Of these, 37 had severe preschool wheeze and 14 were non-wheezers.
In total, 15 (40.5%) of the 37 preschool wheezers were diagnosed with asthma in later childhood compared with just one non-wheezer (7.1%).
Among children with evaluable biopsy specimens, those with asthma (n=8) at school age had a significantly greater median preschool ASM area fraction than those without (n=24), at 0.120 versus 0.066.
Children with asthma at school age also had a significantly greater median preschool ASM volume fraction than those without, at 0.153 versus 0.097.
There were no significant differences between children who did and did not develop asthma regarding preschool reticular basement membrane thickness, eosinophilic inflammation, or ASM mast cell numbers.
Saglani et al conclude: "We have shown, for the first time, that ASM is increased in those preschool children with severe wheeze who go on to have asthma at school age."
However, they add: "The numbers are small and represent children with particularly severe wheeze at preschool age, such that our findings cannot be assumed to be applicable to children with less severe wheeze."
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