The characteristic pathologic features of asthma in adults and school-aged children develop in preschool children with confirmed wheeze between the ages of 1 and 3 years, a time when intervention may modify the natural history of asthma.

Remodeling of the airway wall occurs in adults with asthma, and reticular basement membrane (RBM) thickening is pathognomonic of the asthma process. To investigate whether RBM thickening is present in children with difficult asthma and comparable to that seen in adults with asthma, we used light microscopy to measure RBM thickness in plastic-embedded endobronchial biopsy sections from 19 children with difficult asthma who were prescribed 1,600 microg/day or more of inhaled steroids (age range, 6-16 years), 10 children without asthma (7-16 years), and three adult groups: 8 healthy control subjects (21-42 years), 10 mild steroid-naive subjects with asthma (18-41 years), and 6 adults (3 steroid naive and 3 on inhaled steroids) intubated after a life-threatening attack of asthma (20-64 years). RBM thickness in the children with asthma was similar to that in adults with either mild or life-threatening asthma (median 8.2 [range 5.4-11.1] versus 8.1 [5.8-10.0] and 7.2 [2.8-10.0] microm, respectively) and greater than either adult or pediatric control subjects (8.2 [5.4-11.1] versus 4.4 [3.2-6.3] microm, p < 0.01, and 4.9 [3.7-8.3] microm, p < 0.01). We conclude that RBM thickening is already present in children with difficult asthma and to a similar extent to that seen in adults with asthma. In addition, we find no association with age, symptom duration, lung function, or concurrent eosinophilic airway inflammation.

RBM thickening and the eosinophilic inflammation characteristic of asthma in older children and adults are not present in symptomatic infants with reversible airflow obstruction, even in the presence of atopy.

Exhaled nitric oxide (FE(NO)) has been proposed as a noninvasive marker of airway inflammation in asthma, and may reflect airway eosinophilia. We examined the relationship between FE(NO) and eosinophilic inflammation in endobronchial biopsies from 31 children with difficult asthma (mean age [range] 11.9 [6-17] yr), following 2 wk of prednisolone (40 mg/d). Endobronchial biopsy was also performed in seven children without asthma. Biopsy eosinophils were detected using antibody to major basic protein, and point-counting used to derive an "eosinophil score." FE(NO) readings and suitable biopsies for analysis were both obtained in 21 of 31 children with asthma. Adherence to prednisolone was demonstrated in 17 of these 21. Within this group, there was a correlation between FE(NO) and eosinophil score (r = 0.54, p = 0.03). The relationship was strongest in patients with persistent symptoms after prednisolone, in whom FE(NO) > 7 ppb was associated with a raised eosinophil score. For all patients, FE(NO) < 7 ppb was associated with an eosinophil score within the nonasthmatic range, regardless of symptoms. We propose that FE(NO) is associated with eosinophilic inflammation in children with difficult asthma, following prednisolone, and may help in identifying patients in whom persistent symptoms are associated with airway eosinophilia.