Barrett's esophagus is a change in the epithelial lining of the esophagus from a stratified squamous, nonkeratinized epithelium to a mucus-secreting columnar epithelium is a form of metaplasia.

This condition, called Barrett's espophagus, is caused by chronic acid reflux.

In individuals with chronic vitamin A deficiency, epithelial tissues of the type found in the bronchi and urinary bladder are gradually replaced by stratified squamous epithelium.