Vampire folklore may have been inspired by a rare disease called porphyria, which can cause sensitivity to sunlight and protruding canine teeth, but Dr. Claus Pierach doesn’t like to draw attention to such theories.

Of course, he didn’t help matters when he told me about the treatment he helped invent decades ago.

With human blood. In a laboratory. In a basement.

“We take outdated blood from a blood bank and boil it with glacial acetic acid, which splits certain substances off, sterilizes the blood, and ultimately we have a substance that’s called hematin,” he said.

Pierach is a Minneapolis doctor and one of the world’s experts on porphyria, pronounced “poor-fear-ria.” While he accepts that Halloween is a natural time to talk about the disease and its links to macabre folk tales, he worries that focusing on vampire theories is a disservice to patients suffering its painful and even fatal attacks.

“It is an attractive story if you like fairy tales or spooky stories, but I’m not in favor of making the connection,” he said, “because porphyria affects living people.”

The history of the disease is nonetheless fascinating — both how it got linked to folklore and how Minnesota doctors figured out a way to treat it.

Porphyria results from a chemical buildup in the body that disrupts hemoglobin, the protein that transports oxygen in the blood. Some forms of the genetic disorder attack the skin, causing rashes, pain from sun exposure, increased hair growth and deformities. Other forms attack the internal organs, causing everything from abdominal pains to seizures to disordered thought.

Pierach’s mentor, the late University of Minnesota professor Cecil Watson, developed the first definitive chemical test for porphyria in 1942.

Two decades later, they worked together at the U and at Northwestern Hospital (now Abbott Northwestern) and created hematin, or heme, which restores hemoglobin and prevents or reduces the severity of porphyria attacks. Using human blood instead of animal blood to make heme was in some ways a marketing ploy, so patients wouldn’t be “spooked,” Pierach said, but he laments that it might have led others later to link the disorder with vampires.

In 1985, the New York Times covered a scientific presentation by a Canadian biochemist who theorized that, back in the Middle Ages, sufferers of the disease might have gone outside only at night and instinctively drunk blood for relief. Another symptom, rapid hair growth, might have fueled mythology about werewolves.

Pierach fired off a letter to the Times a day later, calling the theory “irresponsible.” His sensitivity is borne out of patients’ suffering — not just when they have attacks, but when they await them.

“It is not a nice thing to live under the sword,” he said, “and wonder ‘When will it … hit me again?’”