As Chelimsky ran his tests on her hands and feet, it was clear that there was significant nerve damage. The most common cause of this kind of damage was diabetes, but this patient didn’t have that. A pinched nerve in the neck could also cause this kind of injury; so could a deficiency in vitamin B-12. But what caught Chelimsky’s attention was the possibility that the disease had affected not just the nerves he was testing — those that carry information back and forth between the brain and the voluntary muscles of the body — but also the type of nerves he couldn’t test by EMG, autonomic nerves, which innervate the organs like the heart, the stomach, the urinary tract. Many of her other symptoms — the rapid heart rate, being unable to urinate, abdominal pain with no visible cause, even her constipation, which had been so severe that six months before much of her colon was removed — could be caused by damage to the autonomic nervous system. All that added up to just one likely diagnosis.

“Has anyone ever mentioned the word porphyria to you?” he asked. She’d never heard of it. He wasn’t certain that’s what she had; he hadn’t examined her or reviewed her medical records, but the involvement of both types of nerves suggested this rare disease, and he thought she should discuss the possibility with her doctors.

When the patient got home that afternoon, she told her husband that Chelimsky said that she might have something called porphyria. Together the patient and her husband, a pediatrician, went to his library of medical books and began reading up on this rare disease. They read that porphyria was the name of a group of diseases caused by a genetic defect in the way that one part of the red blood cell is made. The oxygen-carrying portion of blood, known as heme, is a complicated molecule made in the liver and the bone marrow. Porphyria is caused when one of the pieces of the anatomical machinery that makes heme is missing. This is the disease that may have given birth to the American Revolution. It’s thought that King George III was suffering from porphyria as he fiddled while the colonies were ablaze with the drive for independence.

As the patient read about the most common symptoms of the disease — episodes of abdominal pain, nausea, vomiting or constipation, weakness, confusion, rapid heart rate, the inability to urinate — it was as if she were reading her own medical history: her entire life seemed to be there on the page of these old medical textbooks. All the strange and terrible symptoms she suffered through, had surgery for, been considered crazy for, were there on the pages she read. Tears flowed down her face. Her husband cried, too. They had, she felt certain, finally found the answer.

It took more than three months for the patient to get a definitive diagnosis. If figuring out this disease was difficult, testing for it was equally so. But eventually, porphyria was confirmed.

Porphyria is a disease of the nervous system. Thus, everything in the body is affected. The patient’s hardworking doctors had been chopping down the trees one by one, treating each ailment in isolation. Dr. Chelimsky, a neurologist, was finally able to step back and see the entire forest.

The children of a person with porphyria have a 50 percent chance of inheriting the disease. Recently the patient’s brother was given a diagnosis of porphyria. And she now realizes that her father, who died six years ago, probably had it as well. It’s painful for her to think of his suffering for all those years without the diagnosis that could have saved his life.

There is no cure for porphyria, but it can be treated. Episodes of pain can be shortened by providing the body with the heme it needs. The patient learned that she could prevent many of the attacks by avoiding the disease triggers — certain drugs and hormones, stress, illness, skipping meals. She told me recently that she has worked hard to make these lifestyle changes. And, she added proudly, she hasn’t had an attack in more than a year.