Bronchiole dilation resulting from chronic infection is present in pneumonia, tuberculosis, bronchiectasis, chronic obstructive pulmonary diseases, sleep apnea, asthma and emphysema. Tuberculosis is caused by tubercle bacilli that has invaded the macrophages resulting into a walling off lesion by fibrous tissue to form the so-called tubercle. Pneumonia is mainly caused by Klebsiella pneumoniae and Streptococcus pneumoniae, infection can spread by extension of bacteria from alveolus to alveolus in the lungs. In this disease process, the gas exchange function of the lungs decline in different stages of the disease.
