For the millions of children and adults with severe food allergies, ingesting even tiny quantities of some of the most basic foods can result in a potentially deadly reaction. Milk, eggs, nuts, fish, shellfish, soy and wheat are some of the most common offenders.
Some people with food sensitivities have something more than just a food allergy. Eosinophilic esophagitis (EoE) is a condition in which exposure to certain foods causes the inappropriate migration of immune cells called eosinophils to the lining of the esophagus, where they release factors that lead to inflammation and swelling. This can result in feeding difficulties and failure to thrive in young children, and difficulty in swallowing in adults. Other symptoms include heartburn, vomiting and food impaction in the esophagus. About one in 10,000 people is thought to have EoE, although some researchers think this may be an underestimate.
Studies indicate that EoE has a strong genetic component, but previous research has linked only one gene to the condition. However, in a recent issue of the journal Nature Genetics, researchers from Cincinnati Children’s Hospital Medical Center and the Children’s Hospital of Philadelphia presented results of a genome-wide associations study of EoE that indicate that a gene known to play a role in asthma and atopic dermatitis (a type of eczema) is also associated with the condition.
A total of 351 people with EoE and 3,140 unaffected controls, all children and young adults of European ancestry, were studied to find genetic variations associated with the condition. The strongest association with EoE revealed by the DNA analysis was with a SNP near the TSLP gene. The slightly less common G version of this SNP was found more often in controls than cases of EoE, suggesting that it confers protection against the condition. Each copy of the G version was associated with 0.53 times odds of EoE compared to having two copies of the A version in the first group studied, and 0.73 times odds in a replication group.
The researchers looked at esophagus tissue samples to learn more about TSLP. They found that the gene is turned on at higher levels in people with EoE, and that there is a correlation between having the protective G version of and lower levels of the TSLP protein.
The TSLP protein is known to regulate inflammatory responses. It is a key initiator of allergic inflammatory diseases and has been shown to be overproduced in atopic dermatitis lesions and asthma-affected lungs. People with EoE often also suffer from these other allergic conditions.
“Eosinophilic esophagitis is a highly allergic disease, and one that is rapidly expanding,” said Jonathan M. Spergel, director of the Center for Pediatric Eosinophilic Disorders at the Children’s Hospital of Philadelphia and a co-first author of the study, in a press release.
“This is the first genome-wide association study done of this disease, and now that we have elucidated a gene pathway, the hope is that physicians can eventually intervene in that pathway and discover a new treatment.”