1063:  ERS: Study of nose and throat reveals why people with COVID-19 may lose their sense of smell

Researchers who have been studying tissue removed from patients’ noses during surgery believe that they may have identified the reason for loss of sense of smell among COVID-19 patients, even when they have no other symptoms.

Investigators noted very high levels of angiotensin converting enzyme II (ACE-2) only in the area of the nose responsible for smelling. This enzyme is believed to be the portal of entry for the coronavirus to get into the cells of the body and cause an infection.

Findings, published in the European Respiratory Journal, offer clues to the high infectivity of COVID-19 and suggest that targeting this particular part of the body could help determine more effective treatments.

While other respiratory viruses generally cause loss of sense of smell by obstructing the airflow due to swelling of the nasal passages, this virus sometimes causes loss of smell when there are no other nasal symptoms.

Investigators used tissue samples from the back of the nose of 23 patients that were removed during endoscopic surgical procedures for conditions such as tumors or chronic rhinosinusitis. Biopsies from the trachea of seven patients were also studied. None of the patients had been diagnosed with COVID-19.

Fluorescent dyes were used on the tissue samples to detect and visualize the presence of ACE2 under a microscope. Investigators compared the levels of ACE2 in different cell types and parts of the nose and upper airway.

They found the most ACE2 on the lining cells of the olfactory epithelium, the area at the back of the nose where smells are detected.

The levels of ACE2 in these cells was found to be 200- to 700-times higher than other tissue in the nose and trachea. High levels were observed in all the samples of olfactory epithelium, irrespective of the condition the patient had been treated for. ACE2 was not detected on olfactory neurons.

The levels of ACE2 were found to be the highest in the part of the nose that is responsible for smell. The results thus suggest that this area of the nose could be the part where the coronavirus is entering the body.

A virus can easily reach the olfactory epithelium, and the very high levels of ACE2 in this part might explain why its so easy to catch COVID-19.

[Source: https://healthcare-in-europe.com/en/news/study-reveals-why-people-with-covid-19-may-lose-their-sense-of-smell.html]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

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