Diagnostic dilemma: Viral infection caused woman not to recognize her own father

The patient: A 28-year-old woman in New Hampshire

The symptoms: In March 2020, the woman developed a high fever, chest tightness, shortness of breath and diarrhea, and she lost her sense of smell and taste. She also experienced coughing fits so intense that they caused her to faint. Based on these symptoms, her primary care provider diagnosed her with COVID-19, although she was not formally tested for the illness due to the lack of diagnostic testing available at the time.

After her diagnosis, she did not seek further medical care due to concerns about out-of-pocket costs, according to a report of the case.

What happened next: Three weeks after her symptoms started, the patient felt well enough to work from home. However, four weeks after that, many of her symptoms returned. She also noticed new feelings of disorientation and felt that "something was off with faces." Her primary care doctor suggested she go to an emergency room, where a CT scan was taken of her brain. The scan didn't show any active bleeding, the report notes, and she was discharged.

In June 2020, the patient spent time with family for the first time since catching COVID-19 and found she could not recognize her father or visually distinguish him from her uncle. She still recognized people by their voices, though.

The patient worked part time as a portrait artist; she used to be able to check her reference photos every 15 to 30 minutes but found she now struggled to hold the details in her mind. She told doctors that "faces are like water in my head," according to the case report.

The patient also had trouble doing everyday tasks, such as navigating her local grocery store or finding her way back to her car in a parking lot. In November 2020, she also started having balance issues and frequent migraines.

The diagnosis: Based on her wide-ranging and relapsing symptoms and her suspected history of COVID-19, doctors diagnosed the patient with post-acute sequelae of COVID-19 (PASC), now known as long COVID. They diagnosed her difficulties with recognizing faces as "face blindness," or prosopagnosia.

Roughly 2.5% of the general population is thought to be born with some degree of face blindness, while others can acquire the condition later in life. The exact number of people with acquired prosopagnosia is unclear, but some estimates suggest roughly 1 in 30,000 people in the U.S. are affected.

Many people with acquired prosopagnosia also have issues navigating familiar spaces. That was also the case with this patient, likely due to the "proximity of brain regions critical for scene and face processing," the case report authors noted.

To assess the extent of the patient's prosopagnosia, doctors had her complete several tests of facial memory, which asked her either to memorize strangers' faces or recognize celebrities' faces. The patient performed markedly worse on these tests than 10 women of similar age who were used as a comparison group.

However, she performed as well as the comparison group on other types of cognitive tests, suggesting her deficits were fairly specific to faces. She also got normal scores on tests of facial perception — the ability to recognize that a face is a face — so her face blindness seemed tied more to memory deficits for faces, the report authors said.

The treatment: The case report does not detail a specific course of treatment, and in general, few treatments exist for face blindness. If there's a clear cause for the deficit — such as a tumor in a key part of the brain for facial processing — addressing that underlying issue can help reverse acquired face blindness.

If the condition ends up being permanent, there are various strategies that can help patients cope. For instance, "perceptual training" can improve patients' ability to identify and remember the features of a person's face. Additional strategies include training people to use other cues, like voices and social context, to identify people.

What makes the case unique: In this patient's case, the report authors suspect that her COVID-19 infection triggered her face blindness either acutely or in the aftermath of the infection.

Various infections have been tied to face blindness; both bacterial meningitis and Whipple disease (caused by the bacterium Tropheryma whipplei) have been flagged as culprits, although such cases are uncommon. In a second known case involving COVID-19, a different person developed face blindness after an infection but had also had a stroke in the right hemisphere of their brain, a known cause of prosopagnosia.

The 28-year-old woman, by contrast, wasn't thought to have suffered a stroke, and it's unclear exactly how COVID-19 led to her facial processing issues.

The case report authors surveyed more than 50 other people with long COVID, to see if they also had signs of face blindness. While many showed general declines in visual recognition and navigational abilities, the group didn't have a specific problem with faces. So while long COVID is known to cause a range of neurological issues, it appears that face blindness is a rare consequence.

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