Eosinophilic gastrointestinal disorders are a group of diseases characterized by inflammation that causes the infiltration of eosinophils in specific regions of the gastrointestinal tract1. The best characterized entity is eosinophilic esophagitis2. Having eosinophils in the gastrointestinal tract can be “normal” (with the exception of the esophagus), because they play a relevant role in the immune response of the mucosa, and so are present in situations, such as allergies to medications or foods, parasitic infections, malignant neoplasms, inflammatory bowel disease, and hypereosinophilic syndrome. However, if a large number of eosinophils are found in the stomach, small bowel, or colon, and other causes of eosinophilia are ruled out, the patient is considered to have a primary eosinophilic disease, such as gastritis, enteritis, or eosinophilic colitis (EoC).

The first descriptions of EoC were made in 19373, and for over 50 years, information had been limited to case reports or case series, but over the past decade, an accelerated rise in its prevalence has been reported1. In a database of more than 35 million subjects in the United States, whose analysis encompassed the time frame of 2012 and 2017, Mansoor et al.4 described a prevalence of EoC of 2.1/100,000 inhabitants. A recent systematic review and meta-analysis that included 10 studies with 13,377 patients, evaluated patients that visited an outpatient clinic for gastrointestinal symptoms and underwent endoscopic studies, describing a prevalence of 1.9% (a 95% confidence interval of 0.575 to 3.894)5. The reason for the rapid rise of the disease is not yet clear, but the environmental elements of diet, lifestyle, alterations of the microbiome, and exposure to allergens, as well as genetics, have been proposed as determining factors. With respect to the genetic factors, even though eosinophilic diseases have been reported more frequently in White populations, the past decade has also seen an increase in such reports in non-White populations.

In the journal’s present issue, in a case series of 683 cases treated for diarrhea at a referral center, Carmona-Sánchez et al.6 reported that 4% had a final diagnosis of primary EoC and it was higher in the patients with diarrhea-predominant irritable bowel syndrome (4.7%). The study is important for numerous reasons. First, it is one of the largest Mexican case series that prospectively and intentionally searched for the diagnosis of EoC. Second, the epidemiologic characteristics are similar to those reported in other case series. For example, male sex was not predominant (unlike that which occurs in eosinophilic esophagitis), the disease mainly affects patients in the fourth and fifth decades of life, abdominal pain and chronic diarrhea are common, and a history of atopy and allergic diseases is considerably higher than in the general population (odds ratio of 3.36). Third, up to 36% of the patients had minimal endoscopic alterations. In all likelihood, the use of novel technologies in endoscopy (such as virtual chromoendoscopy, magnification, artificial intelligence, etc.) makes it easier to detect those alterations and enable the performance of targeted biopsies. Finally, as in other case series, treatment with budesonide at a dose of 9 mg for up to 8-week periods resulted in symptom resolution in more than 70% of the cases.

Even though the need to routinely suspect EoC in patients with chronic diarrhea in the Mexican population is now clear, there are numerous questions that still must be answered. For example, longitudinal studies are needed to better understand the mechanisms of the disease and the long-term results. Its pathophysiology must also be understood, given that transcriptomic analyses have shown differences between eosinophilic esophagitis and EoC, and there is surely variability in relation to the geographic zones, genetics, and lifestyle of each population as well.

In the meantime, we recognize that the rise in EoC means it is here to stay.