Changes in Throat Microbiota Linked to HAE Swelling Episodes

Recent episodes tied to increased levels of Bacteroidetes, Prevotellaceae bacteria

Somi Igbene, PhD avatar

by Somi Igbene, PhD |

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Changes in the number of types of bacteria in the throat are linked to throat swelling episodes in hereditary angioedema.

Changes in the number of certain bacteria in the throat are linked to throat swelling episodes in people with hereditary angioedema (HAE), a recent study has found.

Patients with recent episodes of throat swelling had significantly increased quantities of Bacteroidetes and Prevotellaceae bacteria, with increases in Bacteroidetes associated with severe attacks.

“The associations between throat microbiomes with laryngeal edema [throat swelling] and disease severity in HAE patients may indicate the potential of microbiome-based interventions in the prevention and treatment of HAE episodes,” the researchers wrote.

The study, “Throat microbiota alterations in patients with hereditary angioedema,” was published in the World Allergy Organization Journal.

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Changes in Gut Microbiota May Contribute to HAE Attacks

HAE is a chronic genetic disease marked by recurrent swelling attacks in the neck, throat, abdomen, and skin. There are three types of HAE, depending on the specific mutations a patient carries. Although types 1 and 2 are caused by mutations in the SERPING1 gene, the severity of the disease varies significantly between people. The reason for this is not known.

Microbiota consist of different microorganisms — bacteria, viruses, and fungi — that contribute to different aspects of human health. Certain body parts, such as the gut, mouth, and genitals, have their own microbiota, and scientists continue to see that microbiota changes contribute to various diseases. Indeed, previous HAE studies have linked changes in gut microbiota — specifically a decrease in Firmicutes and an increase in Proteobacteria — with abdominal swelling attacks.

However, the characteristics of throat microbiota in people with HAE have not been studied and the relationship between these microbes and throat swelling attacks is unknown, leading scientists in China to analyze 36 HAE patients (22 females and 14 males) and 17 healthy family members (six females and 11 males), who served as controls.

The team collected throat swabs from all participants after confirming that none had any throat infection or disease in the previous three months, had taken antibiotics within the last two months, or used antiseptic mouthwash within 24 hours of the swab collection.

After extracting DNA from the swabs, researchers used a gene sequencing technique to analyze the numbers and types of bacteria in the samples.

Participants were divided into three groups according to when they had their last attack (within a month, more than a month ago, or never) and where it occurred (throat, gut, or skin). They also completed a visual analog scale (VAS) to rate the severity of their most recent episode.

Patients had a mean age of 41.9 years. The majority (94.4%) had type 1 HAE, and the remainder had type 2. Half had an HAE episode within the last month; 38.9% had throat swelling, 22.2% had abdominal swelling, and 83.3% had skin swelling.

More than half (55.6%) had never received long-term prophylaxis (treatment to prevent an attack), while 44.4% were receiving Danocrine (danazol) for long-term prophylaxis.

The composition of throat microbiota was similar in all patients, with Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, and Actinobacteria being the most dominant and accounting for more than 95% of bacteria. Danocrine use did not influence throat microbiota composition.

Patients with a recent throat attack had significantly increased Bacteroidetes and Prevotellaceae numbers than those who didn’t have recent attacks. Increases in Bacteroidetes were also linked to attack severity.

Although those with recent gut attacks had slightly increased numbers of Bacteroidetes than those without recent episodes, this increase was not considered statistically significant. There also was no difference in the types or numbers of throat bacteria between patients with and without recent skin episodes.

The study’s small sample size and its inability to match every patient to a healthy control were noted by researchers as limitations in their analyses.

“We reported alterations of the throat microbial communities in HAE patients and explored the correlation between bacteria and edema severity, which may shed light on understanding the disease course and developing new therapeutic strategies for HAE,” the researchers wrote, noting more studies with larger sample sizes were needed to confirm their findings.