'Face blindness' could be rare long COVID symptom, case report hints

"Face blindness," or the inability to recognize faces, may be a rare symptom of long COVID, a new case report suggests.

A case report published in March in the journal Cortex suggests a possible link between long COVID and selective face recognition problems, but, for now, it's unclear if people other than the report's subject have developed the condition after a bout of coronavirus infection.

Annie, the case report subject, fell ill with symptoms consistent with COVID-19 in March 2020. That June, meeting her family for the first time since the onset of her illness, she couldn't recognize her father's face. As a part-time portrait artist, Annie also noticed that she could no longer hold faces in her mind, having to continually depend on reference photos to draw, rather than checking them a few times an hour, as she'd previously done.

Face blindness, or prosopagnosia, is a condition that an estimated 3% of the population are born with, and roughly 1 in 30,000 acquire as a result of damage to regions in the brain specialized for processing faces, such as the fusiform gyrus. In Annie's case, she apparently acquired face blindness after falling ill with COVID-19. Annie also reported difficulties in navigating familiar spaces, such as her local grocery store. Navigational problems like this can often co-occur with face blindness.

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It is not the first time that an infectious disease has been associated with acquired face blindness. Cases have been reported following bacterial meningitis, which causes inflammation of the brain and spinal cord, and Whipple disease, another bacterial infection that can affect the nervous system, although such cases appear rare.

Another case of a person developing face blindness after COVID-19 infection was reported in a 2021 study in the journal Acta Neuropsychologia. That patient, however, had also suffered a right hemisphere stroke, which is commonly associated with acquired prosopagnosia.

"For most people, there is no known cause," said John Towler, a lecturer in psychology at Swansea University in the U.K., who was not involved in Annie's case.

Researchers at Dartmouth College in the U.S. conducted assessments to better understand Annie's problems with face recognition. These included four face identity memory tests gauging Annie's ability to recognize and remember both celebrity's faces and random, new-to-her faces. Compared with a control group of 10 women similar to Annie in age, she performed significantly worse on all four tests.

Annie also showed other symptoms of long COVID, including fatigue and brain fog. However, it is unlikely that her prosopagnosia symptoms arose from a general decline in cognitive function. Her impairment appeared to be highly specific to facial recognition; additional tests showed that her abilities to detect faces, face identity perception (the ability to perceive and cognitively process a face), recognize objects and scenes (such as houses and natural scenes), and retain non-visual memories were spared.

"It's not necessarily surprising that a disease that has such a profound impact on the brain can lead to impairments. What is really interesting is that it is such a selective and highly specific impairment," said Marie-luise Kieseler, lead author of the study and a doctoral student at Dartmouth.

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Even in mild cases, COVID-19 has been linked to structural changes in the brain. However, research so far indicates that the brain structures such as the limbic and olfactory cortical system are those most affected by the coronavirus.

It is unclear exactly how COVID-19 might have contributed to Annie's sudden face blindness. Annie's case raises the question as to whether other people with long COVID may be affected with similar symptoms.

To begin investigating this, the researchers at Dartmouth collected self-reported data from long COVID patients. A majority of this group indicated their overall visual recognition — not specifically related to faces — and navigation capabilities had declined since their illness onset.

Since the pandemic, neither Kieseler nor Towler has noticed an increase in people coming forward with symptoms of face blindness. However, symptoms of face blindness exist on a spectrum, and mild cases, where the inability to recognize faces may not be so severe, may go unreported. "If you only decline mildly, that might not be your main concern, especially if you are dealing with a lot of other things due to COVID," Kieseler said.

In future research projects, including brain imaging studies, the team plans to work with more people who've developed face-processing problems after catching COVID-19 to better understand the link between the infection and face blindness.

Treatment for face blindness is limited, although this may change. Jodie Davies-Thompson, another lecturer of psychology at Swansea, has developed a training program for improving face discrimination in both developmental and acquired face blindness. Towler said that they've seen improvements in specific face perception tasks among people in the program, but further development is needed to ensure these improvements translate to real-world scenarios.