Few studies have evaluated the asthmatic airway in childhood. The aim of this study was to assess the histopathological changes occurring in the bronchi of children with moderate asthma using light and electron microscopy.

Bronchial biopsy specimens from 10 children with moderate asthma (seven boys) of mean (SD) age 9.3 (3.8) years (range 5–14) were examined by light and electron microscopy. Patients had not had a respiratory infection for at least one month and they had not been treated with steroids or sodium cromoglycate for four weeks before the study. Bronchoscopy was performed under general anaesthesia using a Karl Storz rigid paediatric bronchoscope. Biopsy materials were stained with uracyl acetate and lead citrate and evaluated under a Zeiss-10 electron microscope and light microscope.

The most important finding was thickening and hyalinisation of the basement membrane in nine patients. The ciliated epithelial cells showed loss of cilia in some cases. Overactive fibroblasts were consistently found. Six patients had degranulating mast cells and lymphocyte infiltration in the submucosa. Eosinophils were seen in only one biopsy sample.

Children with moderate asthma develop bronchial inflammation similar to the reaction observed in adults. However, in our study the inflammation was rich in lymphocytes rather than eosinophils.