Eosinophils in the gastrointestinal tract: how much is normal?

The normal density of eosinophils in the digestive mucosa of children has been rarely addressed despite being important to provide baseline counts for the diagnosis of eosinophilic gastrointestinal disorders (EGID). Histopathological criteria for EGID remain undefined and there has been little consistency of results in different populations. We aimed to establish the eosinophil density of the normal digestive mucosa in a paediatric population submitted to endoscopic procedures with normal histological features. Biopsies from endoscopies of 33 patients were evaluated. Quantification of eosinophils was performed manually. Review of the pathology reports confirmed absence of abnormality in the biopsy specimens. Counts were expressed in eosinophils per high power field and per mm2. Oesophagus (n = 33): eosinophils were uniformly absent in all biopsies. Stomach: counting was performed, separately, in the superficial and deep lamina propria of the fundus (n = 13), corpus (n = 13) and antrum (n = 16). Mean eosinophilic density was higher in the deep lamina propria. Small intestine: eosinophil counts revealed 18.1 ± 17.0, 14.4 ± 12.0, and 51.5 ± 35.3 in the lamina propria of the bulb (n = 13), D2 (n = 13), and ileum (n = 16), respectively. Large intestine: the highest peak count was observed in the caecum (125 mm2; n = 16) with a mean of 51.8 ± 33.5. The eosinophil counts were lower in the ascending (n = 16; 40.9 ± 27.4), transverse (n = 14; 34.3 ± 21.9), descending (n = 15; 40.0 ± 26.6), and sigmoid (n = 17; 25.8 ± 17.8) colon and in the rectum (n = 17; 13.9 ± 10.1). These data provide a baseline count and distribution of eosinophils in the gastrointestinal tract of paediatric patients with normal mucosa, thus expanding the scarce published data.