5 Medical Mysteries Doctors Still Haven’t Solved

The Dancing Plague of 1518

In July of 1518, a woman in Strasbourg — now part of France, then part of the Holy Roman Empire — stepped into the street and started to dance. She kept going until she collapsed from exhaustion, then started up again. More people started to join her, and a week later, there were more than 30 dancers, unable to stop even when overexertion set in and they started hurting themselves. Local leadership thought the solution might be more dancing, so they brought in dance halls, musicians, and even professional dancers. The issue, predictably, got worse, and eventually hundreds of people were afflicted. Some died of heart attacks and strokes. Strangely, this isn’t even the only time this happened — just the best-known case.

At the time, doctors and clergy thought the culprit was demonic possession or “hot blood.” Modern theories include stress-induced mass hysteria or a psychoactive mold called ergot that grows on rye (and which some have also blamed for contributing to the Salem witch trials).

The Mysterious 19th-Century Exploding Teeth

In the early 19th century, modern dentistry was basically in its infancy, which may be why nobody knows what caused several cases of exploding teeth. In 1817, a Pennsylvania reverend had a toothache so bad that he was, according to his dentist, “boring his head on the ground.” The next morning, his tooth burst apart with a sharp cracking sound and the pain was gone.

One exploding tooth is strange, but this wasn’t an isolated incident. Three more cases popped up in America in 1830, 1855, and 1871, and a few were recorded in England as late as the 1920s.

In 1860, one dentist theorized that gas from tooth decay was building up and causing the teeth to explode. Modern dentists have suggested that it was an issue with the varieties of metals used for fillings at the time. Both are pretty unlikely scenarios, and the cause remains a mystery.

What Plagued Ludwig van Beethoven?

Composer Ludwig van Beethoven famously started losing his hearing in his late 20s, and although he kept making music for another three decades, his affliction caused some severe depression. His lesser-known ailments certainly didn’t help, either; in his early 20s, he developed severe gastrointestinal symptoms that lasted the rest of his life. Overall, his symptoms were bad enough that he hoped his malady would be studied after his death. He died at the age of 56 with damage to his liver, kidneys, and pancreas after contracting pneumonia. Historians have spent the last 200 years trying to figure out his underlying illness, suggesting everything from lead poisoning to syphilis to celiac disease. DNA analysis from locks of his hair hasn’t turned up anything conclusive (and has just created some more mysteries), but it did reveal a genetic predisposition to liver disease.

The Sleeping Sickness of the 1920s

In 1915 or 1916, doctors in Europe started seeing patients with a mysterious set of symptoms. The condition would start out as a headache, fever, and sore throat before declining into a bevy of neurological symptoms such as double vision or tremors. Around 1 million people eventually developed encephalitis lethargica, or sleeping sickness — unrelated to African trypanosomiasis, which is also sometimes called sleeping sickness.

Eventually, many patients became catatonic or developed debilitating movement disorders that would keep them institutionalized for the rest of their lives. Some patients were revived briefly in 1969 with an experimental Parkinson’s drug, but eventually the symptoms returned. After killing hundreds of thousands of people, the disease all but disappeared in the late 1920s. Around 80 cases have been reported since 1940, but since the diagnostic criteria varies, the diagnoses may be unreliable.

Water Allergies

This affliction is more modern — it was first described in 1964. Technically known as aquagenic urticaria, it involves itchy, stinging welts that erupt within a couple of minutes after the sufferer’s skin touches water. (Drinking water usually seems to be fine). Only 37 cases have ever been reported. Scientists don’t understand what causes it: It might be a response to some kind of toxin in the water, a sensitivity to the ions in water, or some kind of histamine response. There’s no cure, only symptom management (like applying petroleum jelly before showering).