A 53-year-old man comes to the emergency department due to severe heartburn and difficulty swallowing for the last few weeks. He has had mild to moderate heartburn for several years and has tried weight loss, elevating the head of his bed while sleeping, and several months of proton pump inhibitor therapy. Other medical problems include hypertension and hypothyroidism. Temperature is 36.7 C (98.1 F), blood pressure is 130/80 mm Hg, pulse is 78/min, and respirations are 16/min. BMI is 25 kg/m². Physical examination is unremarkable. An upper gastrointestinal endoscopy is performed, and esophageal biopsy shows columnar epithelium with interspersed goblet cells. A similar adaptive response can be seen in which of the following scenarios?

Question

Quizplus · Accepted Answer

11ec160b_39f4_f98f_9249_4f4bce6592e6_MD0001_00 The esophagus is normally lined by nonkeratinized, stratified squamous epithelium. However, chronic exposure to acidic stomach contents can damage the epithelial surface and result in the release of cytokines and growth factors that cause esophageal stem cells to differentiate into an alternate epithelial cell type (intestine-like columnar cells) better suited for an acidic environment. The substitution of one differentiated epithelial cell type for another in response to adverse environmental conditions is called metaplasia. Metaplasia is also seen in the trachea and bronchi of chronic cigarette smokers where the irritative effect of smoke leads to the replacement of normal ciliated columnar cells with heartier stratified squamous epithelium. Although this substitution reduces epithelial injury, it also eliminates the cell types that contain cilia and produce mucus, which increases the risk of respiratory infection. Metaplasia is a reversible condition, but continued environmental stress can lead to malignant transformation (metaplasia → dysplasia → invasive cancer). For instance, the metaplasia seen in the distal esophagus in response to chronic acid exposure (Barrett esophagus) is associated with a high risk of malignant transformation into esophageal adenocarcinoma. (Choice B) Psoriasis is characterized by hyperplasia, an increase in the number of cells within a tissue due to hormones or growth factors. Histology will show hyperproliferation of the dermis with epidermal thickening (acanthosis) and prolonged downward thickenings between dermal papillae ("rete ridges"). (Choice C) Irregular moles (eg, melanoma, atypical mole) are likely to contain dysplastic cells. Dysplasia is characterized by abnormal epithelial cellular architecture and irregular cellular growth. In metaplasia, one mature, differentiated cell type is replaced by another. (Choice D) Hypertrophy is an increase in the size, but not number, of cells. Left ventricular hypertrophy can occur with aortic stenosis due to higher systolic pressures necessitating increased myocardial effort. (Choice E) Atrophy is a reduction in cell size and number; it can occur in skeletal muscles following a period of immobility (eg, bedbound patient). Educational objective: Metaplasia is the substitution of one differentiated cell type for another due to the presence of an adverse environmental stimulus. It is often seen in the bronchi of chronic cigarette smokers (substitution of ciliated columnar epithelium with stratified squamous cells) and the distal esophagus of patients with chronic gastroesophageal reflux (substitution of stratified squamous epithelium with intestinal columnar cells). Metaplasia can lead to subsequent dysplasia and malignant transformation. __________ References: Common questions about Barrett esophagus. (http://www.ncbi.nlm.nih.gov/pubmed/24444576) Recent developments in pathogenesis, diagnosis and therapy of Barrett's esophagus. (http://www.ncbi.nlm.nih.gov/pubmed/26074687) Squamous metaplasia is increased in the bronchial epithelium of smokers with chronic obstructive pulmonary disease. (http://www.ncbi.nlm.nih.gov/pubmed/27228128)

A 53-Year-Old Man Comes to the Emergency Department Due to Severe