Food allergy series: Eosinophilic esophagitis (Part 2)

Diagnosis of EoE can be difficult. Endoscopy with biopsy is the only reliable method currently available. Often in these patients, the esophagus may look unremarkable, so biopsies are recommended regardless of gross appearance. 2-4 biopsies from the proximal and distal esophagus should be collected. Biopsies of the gastric antrum and duodenum may also be taken to rule out other conditions.

Fibrosis of the lamina propria is present in most biopsies of both child and adult patients. Though less prevalent, this finding is still found sometimes in GERD cases. Basal zone hyperplasia, elongation of rete pegs and dilated intercellular spaces are EoE associated findings. Additionally, mast cells are increased in biopsies from EoE patients more so than GERD patients. IgE bearing cells are found more often in EoE than GERD.

There is some dispute over whether the peak value (the cell count in the single high powered field with the most eosinophils) is more representative than the average value (the average of cell counts in several high powered fields.) Some studies have found a correlation between eosinophil count and symptom presentation, while others have not. There are also some patients with active eosinophilic inflammation in the esophagus with few symptoms.

Other diagnostic methods should be included to rule out other conditions.   Esophageal manometry and pH testing in EoE children demonstrated that dysfunctional peristalsis correlated with difficulty swallowing. Esophageal manometry with pressure topography can reveal abnormal pressurization patterns in EoE that are not found in GERD. Endoscopic ultrasound has shown thickening of both the muscles and the mucosa in EoE. Impedance planimetry, a method that measures both pressure and volume changes, has recorded significant changes in compliance and distensibility of the esophageal wall in EoE patients. Barium contrast swallow testing was normal in 12/17 children with EoE, including four who had required endoscopy for food impaction. X-ray can detect stricturing of the proximal cervical esophagus. Some studies have linked motility issues to EoE, while others have found the opposite.

pH testing is usually undertaken to exclude GERD. In multiple studies, transnasal and wireless capsule pH measuring systems have shown variability in acid pH. When coupled with impedance testing, pH testing seems to correlate better with symptoms, but this has not been fully investigated yet. In children, both acid and non-acid reflux is comparable to controls.

40-50% of EoE patients have an increase in circulating eosinophils. When EoE is effectively treated with topical corticosteroids, peripheral eosinophilia has been shown to decrease. One study noted that in EoE patients, esophageal eosinophils display HLA DR, which means that they act as antigen presenting cells. Antigen presenting cells recruit other cells in the immune system and generate a strong inflammatory response.

Periostin, an extracellular matrix protein, is increased in the esophagus of EoE patients. Importantly, it correlates with eosinophil levels in EoE patients. Expression of eotaxin 1 and 3 is also increased in EoE. Fibroblast growth factor 9, IL-13, IL-15 and TGFB-1 can be elevated in both EoE and GERD.

A crucial finding in EoE research was the characterization of a signature transcriptome, which measures which genes the cells are using and which proteins they are making. This transcriptome is distinct from nonspecific chronic esophagitis, which has a peak eosinophil count or 6 or fewer eosinophils/hpf. Studies have demonstrated that the transcriptome can distinguish from GERD. Eotaxin 3 is hugely overexpressed in EoE patients. IL-13 is also overexpressed, with data to indicate that it may be the key regulator in EoE disease processes. In patients who have successfully achieved symptom remission, abnormal gene expression has returned to normal. However, some genes in epithelial cells continue to be expressed abnormally, which may factor into relapse.

Genetic studies have revealed that the first genome wide susceptibility locus for EoE is at 5q22. The study that found this common variable included 550,000 common genetic variants collected from various institutions. In this susceptibility locus lie genes associated with thymic stromal lymphopoietin (TSLP), a cytokine that influences behavior of Th2 cells. In a second study that looked at 53 potential genes that affected allergic or epithelial responses, or both, the TSLP gene was also identified as a susceptibility locus for EoE. This continued to be true when the data was controlled for atopic conditions. The TSLP receptor gene on the X chromosome has also been tied to EoE in male patients. These findings make a strong case for EoE as a Th2 mediated disease.

Another genetic factor found to be overrepresented in EoE patients was a common deletion variant in the filaggrin gene, 2282del4. This mutation has been associated strongly with atopic dermatitis. However, even in EoE patients who don’t have atopic dermatitis, this genetic variant is found more frequently than in the general population.

 

References:

Liacouras, Chris A., et al. Eosinophilic esophagitis : Updated consensus recommendations for children and adults. J Allergy Clin Immunol 2011, pp. 3-20.

Furata, Glenn T., et al. Eosinophilic esophagitis in children and adults: a systematic review and consensus recommendations for diagnosis and treatment. Gastroenterology 2007; 133:1342-1363.