KEYSTONE, COLO. — Does the sharp escalation in diagnoses of eosinophilic esophagitis in the past several decades reflect a true emerging epidemic of a relatively new disease, or is it merely an artifact of greater physician recognition?
The truth most likely lies somewhere in between, Dr. David M. Fleischer asserted at a meeting on allergy and respiratory disease sponsored by the National Jewish Medical and Research Center.
Eosinophilic esophagitis was first described in 1977. Epidemiologic studies suggest the worldwide incidence in both children and adults is climbing and may now exceed that of inflammatory bowel disease.
Eosinophilic esophagitis has been characterized by some as “eczema of the esophagus.” And indeed, the increase in the disorder mirrors the well-documented rise in recent decades of the more traditional manifestations of atopy—food allergy, atopic dermatitis, allergic rhinitis, and asthma.
How common is eosinophilic esophagitis? When gastroenterologists at the Karolinska Institute, Stockholm, conducted a population-based study in which they performed esophagogastroduodenoscopy in 1,000 randomly selected adult volunteers, they found 1.1% had 15 or more intraepithelial eosinophils per high-power field (Gut 2007;56:615–20), thereby fulfilling the pathologic portion of the diagnostic criteria for eosinophilic esophagitis.
Pediatric gastroenterologists in Ohio estimated the prevalence of eosinophilic esophagitis in youths up to age 19 years at 4 per 10,000 in 2003 (N. Engl. J. Med. 2004;351:940–1). And a blinded retrospective evaluation of esophageal biopsies at a tertiary pediatric gastroenterology clinic in Western Australia showed a rapidly increasing prevalence of eosinophilic esophagitis, from 0.05 cases per 10,000 children in 1995 to 0.89 per 10,000 in 2004 (Arch. Dis. Child. 2006;91:1000–4).
But with the exception of the Swedish study, these reports are susceptible to ascertainment bias. Moreover, while the annual number of PubMed citations on eosinophilic esophagitis has grown exponentially since 1978, only 29% of them were original studies; the rest were case reports or review articles.
That rate of growth in turn suggests awareness of eosinophilic esophagitis on the part of gastroenterologists, allergists, and pathologists is growing at a considerably faster pace than any actual advance in scientific understanding.
The implication is that increased physician recognition of the GI disorder is contributing—to an as-yet uncertain extent—to the apparent rise in incidence and prevalence, observed Dr. Fleischer, a pediatric allergist at the center.
Although the epidemiology of eosinophilic esophagitis is incompletely understood, it is known that males account for 75%–80% of cases, consistent with the strong male predilection for food allergy. It is clearly an allergic disease. Most affected patients have a personal and family history of allergic disease. Some also display seasonal variation in their GI symptoms.
Moreover, roughly 80% of patients with eosinophilic esophagitis have elevated serum total IgE and display sensitization to food or environmental allergens on skin prick tests, patch testing to foods, and/or RAST testing, Dr. Fleischer continued.
Biopsy specimens of esophageal mucosa in affected individuals show eosinophils, T cells, and mast cells, suggestive of chronic TH-2-associated inflammation. Elevated levels of TH-2 cytokines such as interleukin-5 and interleukin-13 are also present.
Further underscoring the allergic nature of eosinophilic esophagitis is the fact that most affected patients respond to antiallergy therapy, whether it be swallowed inhaled corticosteroids or food elimination or elemental diets, Dr. Fleischer noted.