*In animals, it is most commonly a sequel of '''widespread fibrosis in the lung''' or [[Bronchitis#Chronic bronchitis|chronic bronchitis or bronchiolitis]] which stimulates hypertrophy in the walls of small arteries | *In animals, it is most commonly a sequel of '''widespread fibrosis in the lung''' or [[Bronchitis#Chronic bronchitis|chronic bronchitis or bronchiolitis]] which stimulates hypertrophy in the walls of small arteries |