Since the 1950s, several investigators have published reports of patients with dysphagia who had associated lower esophageal ringlike constrictions, but each investigator had a different opinion as to the cause and nature of these rings. In 1953, Ingelfinger and Kramer believed that these rings occurred as a result of a contraction by an overactive band of esophageal muscle  ; however, Schatzki and Gary believed that these rings were fixed and not contractile.  Some of this controversy may be related to the confusion of categorizing muscular and mucosal rings under the same entity, as concluded by Goyal et al. [3, 4, 5, 6]
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Two rings have been identified in the distal esophagus. The muscular ring, or A ring, is a thickened symmetric band of muscle that forms the upper border of the esophageal vestibule and is located approximately 2 cm above the gastroesophageal junction. The A ring is rare; furthermore, it is even more rarely associated with dysphagia. On the other hand, the mucosal ring, or B ring, is quite common and is the subject of discussion in this article. The B ring is a diaphragmlike thin mucosal ring usually located at the squamocolumnar junction; it may be symptomatic or asymptomatic, depending on the luminal diameter.
The pathogenesis is not clear, and patients typically present with intermittent nonprogressive dysphagia for solids. Fortunately, most patients respond well to initial and repeat dilatation therapy. A small number of patients may have stubborn rings that require more aggressive endoscopic or surgical intervention.
The pathogenesis of Schatzki rings is not clear, and at least 4 hypotheses have been proposed. These hypotheses may not be mutually exclusive. Proposed hypotheses are as follows:
- The ring is a pleat of redundant mucosa that forms when the esophagus shortens transiently or permanently for unknown reasons.
- The ring is congenital in origin.
- The ring is actually a short peptic stricture occurring as a consequence of gastroesophageal reflux disease.
- The ring is a consequence of pill-induced esophagitis.
Data supporting or refuting the first 2 hypotheses are few.
Data about the association of gastroesophageal reflux disease and rings are inconclusive or contradictory. It has been hypothesized that the ring acts as a protective barrier against further reflux. However, in one recent study involving 20 patients, no significant differences were noted in any of the reflux parameters measured before and after dilation. In fact, it was interesting to note that thick rings may actually decrease esophageal acid clearance, especially in the supine position, thereby increasing esophageal acid exposure.
The last hypothesis was based on a chance observation in one study showing that 62% of patients with rings had ingested medications known to cause pill-induced esophagitis.
In some studies, the severity of symptoms has clearly been demonstrated to correlate with the luminal diameter. Dysphagia predictably occurs in patients with a luminal diameter less than 13 mm and may vary between 13-20 mm, depending on the size and type of bolus.
Schatzki ring is quite common and may be found in as many as 15% of all patients undergoing barium swallow studies; however, few of these patients exhibit any symptoms of dysphagia.
No data are available.
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No mortality has been ascribed to this entity.
Morbidity is variable. Most episodes of dysphagia are short lived, and intervening periods between episodes may vary from weeks to months or even to years.
No known race predilection exists.
No known sex predilection exists.
Although no known predilection for a specific age group exists, most patients are older than 40 years at presentation. It is relatively rare in children. 
In a retrospective study (2000-2009) that included 18,668 gastrointestinal or esophageal imaging studies in 15,410 children and young adults, Towbin and Diniz found 25 patients (0.2%) with a confirmed diagnosis of Schatzki ring.  Hiatal hernia (n=24/25; 96%), eosinophilic esophagitis (n=10/25; 40%), and gastroesophageal reflux (n=10/25; 40%) were commonly associated with Schatzki rings. The investigators suggested clinicians consider endoscopy and biopsy in all children with Schatzki ring owing to the relatively high incidence of eosinophilic esophagitis in their analysis. 
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