One of the best natural side effects of having a show that has run for nearly 60 years is that the universe gets added to and improved constantly. Star Trek has been around for so long now that it is packed full of history, cultures, alien races, and even political structures that rival those of today. All of these elements add together to make the fictional world feel real.
Not only have the shows created and introduced a wide range of aliens over the years, but they have also fleshed out each unique civilization to the point where they even have their own terrible diseases and ailments. Once such alien specific disease is that of Bendii syndrome — but what exactly is it?
This rare illness is one specific to the pointy-eared Vulcan people. The race is known throughout the galaxy as strict followers of logic and emotional suppression (and also known for having a very good sense of smell). It is not a common ailment, but for those it does affect, the consequences are severe. It’s a neurological illness that affect only older Vulcans, usually those over the age of 200. (It’s important to remember that Vulcan live a lot longer than humans do, and it is common for Vulcans to live this long.) For a long time throughout their history, there was little evidence that the illness even existed. Many believed it to be a myth, as there was not a single-recorded case of it for a few hundred years. That is, until Ambassador Sarek, the father of Spock and Discovery's Michael Burnham, fell ill with the condition in the year 2366. This led to his death just two years later.
The illness is very hard to hide. Due to its neurological nature, it directly targets the Vulcan sufferer's personality and the part of the brain that controls inhibition. The earliest symptom of the disease is an increased lack of control over emotion, resulting in emotional outbursts as well as uncontrollable fits of irrational anger. The Vulcan would often lose all control and become a danger to others, returning to their ancestral way, before the adoption of logic and control. In this primal state, the Vulcan predecessors had run amok, killing both others and themselves in constant civil wars. As the illness progressed, these fleeting moments became more and more frequent, eventually leading to the sick Vulcan’s complete loss of control.
Another dangerous side effect of the syndrome was that due to the Vulcans' natural affinity for telepathy, their symptoms could also be projected onto others. Many Vulcans would be able to resit these projected persuasions of emotional abandon. However, it could also affect non-Vulcans, people who were normally immune to the syndrome. These emotions would often cause anger outbursts and even violence. The only way to control these projections was to have another telepathically gifted Vulcan present to mediate the effects, effectively suppressing the syndrome's telepathic influence. This worked most of the time; however, if a Vulcan affected by Bendii syndrome was particularly distressed, their projections would overpower the telepath. They coud then affect everyone, sometimes even other Vulcans.
The syndrome is untreatable and usually fatal, but the worst part is how it completely debilitates its victims, both physically and mentally. The Vulcans spend their entire lives constructing their personality and appearance, heralding logic and control over all else. They pride themselves as a race of emotionless icons. All this flies out the window as the syndrome begins to take hold. Everything the person has prided themselves on over the years is stripped away in a way that, for a Vulcan, is the most humiliating way possible. To be uncontrollably emotional in public would be mortifying for most Vulcans, but for people in power such as Ambassador Sarek, it would have been societal suicide.
While many liken the syndrome to Alzheimer’s, a similar neurological disease that slowly strips away all control and sense of self, Bendii syndrome is arguably worse. It affects specifically what all Vulcans prize most: their emotional control. It is such a characteristic of their species that without it, the victims of the syndrome don’t live for long.
Bendii syndrome is a great example of how Star Trek has invested serious time into developing its aliens and cultures. Not only do they have unique appearances (despite all being humanoid), governments, histories, but they also have their own specific ailments. Vulcans have been a part of the franchise for so long now that it makes sense that the writers of the show have divulged a plethora of information about them over the years. They have become an exceptional example of how world-building can breathe life into a completely fictional species, to the point where everything feels real.