[Pathological ultrastructural findings in the epithelium of the respiratory passages in children and adults with repeated and chronic respiratory diseases (author's transl)].

The ultrastructure of the respiratory passages epithelium of children, adolescents and older adults suffering from repeated or chronic respiratory disease was studied in the material obtained as a small excision during bronchoscopy. The findings were classified into 4 groups according to the character of the ultrastructural changes found in the epithelium. In large bronchi was found: I--a completely unaltered pseudostratified columnar ciliated epithelium, II--a pseudostratified columnar epithelium with various signs of pathological alteration, III--an altered pseudostratified columnar epithelium with first ultrastructural signs of the development of squamous metaplasia, IV--a developed stratified squamous epithelium. In our opinion, in the respiratory passages of children and adolescents, even if they suffer from repeated respiratory diseases, the pseudostratiified ciliated epithelium persists however damaged to various degree. These patients were classified into the second or at most into the third group. The observation of fully developed squamous metaplasia is reserved to older patients with longer history of chronic respiratory disease.