Many children, at some point, experience ear infections. Ear infections have been well-recorded through history, with early mentions in the writing of Hippocrates, the ancient Greek physician. In the 1850s, researcher Adam Politzer suggested that the cause of middle ear infections, or otitis media (OM), is due to blockage in the Eustachian tube.
Because the Eustachian tube is much smaller in younger children, 75% of otitis media cases occur before the age of 10. In 1938, researcher A.E. Schlanser proposed that genetics was “the greatest single factor in the causation of otitis media.” Now, many decades later, new studies have linked genetics to middle ear infections.
In a study from Baylor College, a team of international researchers found that individuals with a variant in the gene A2ML1 were more likely to suffer from ear infections of the middle ear. Dr. Regie Lyn Santos-Cortez, lead researcher on this study, was trained as an otolaryngologist in her native Philippines. During a medical trip to an indigenous area of the Philippines, Dr. Santos-Cortez was astonished to find that a large number of inhabitants of this area suffered from middle ear infections.
With this foundation, Dr. Santos-Cortez focused the Baylor study on a group of 175 indigenous Filipino subjects who were native to the same vicinity and experienced high levels of middle ear infections. With environmental factors and lifestyles reduced as a major influence, researchers were able to hone in on the genetics. They found that 80% of people with a variance in the A2ML1 gene had suffered from otitis media at some point in their lives.
Ear infections occur when there is mucus of fluid buildup in the Eustachian tube of the ear, due to colds or infections. Known commonly as “glue ear,” ear infections may cause mild to moderate hearing loss in children. In most occurrences of otitis media, middle ear surgery is required to drain the fluids. With this new genetic link identified, researchers are hopeful that that there will be other options to treat OM than surgery.
The key to understanding the A2ML1 gene is studying the role it plays. This particular gene controls the production of a protein which blocks proteases, an enzyme which could cause damage to the middle ear. Researchers found that subjects in this study had a variance on the A2ML1 gene, which causes a deviation from this normal protein production process, thus leading to a higher occurrence of middle ear infections.
Interestingly, researchers found similar cases of genetic variance in children of Hispanic and European heritage in Galveston, Texas, with no apparent relation to the 175 Filipino test subjects. This discovery creates a fuller picture of genetic inheritance through the lens of colonialism. They surmised a potential link between Spanish colonists in the Philippines to connect subjects of Filipino and Hispanic-European heritages.
As Dr. Santos-Cortez and her colleagues continue their research on the role of the A2ML1 gene and susceptibility to middle ear infection, they hope to develop new solutions to treating otitis media to avoid the evasiveness of surgery in young children and simultaneously, to prevent early childhood hearing loss.