When I met Megan, I was worried—really worried. She was 22, and I had been asked to evaluate her tremors. Her medical history included depression, anxiety, and anorexia, yet she was functioning quite well, except for the shakes that had been getting worse and were now constant.

At first, only her hands had been involved. Later, her legs and head began shaking as well. Although she was rarely tremor-free, the shaking seemed to be worse when she was active; her legs shook when she drove a car, and her handwriting was noticeably sloppy. She wasn't sure whether her tremors were present during sleep. During our initial interview I also discovered that her symptoms weren't limited to the shakes. Several months after the tremor started, Megan began to drool, and it seemed to get worse at night. Her extremities had become stiff, and her arms didn't swing naturally when she walked. She felt dizzy and off-balance and seemed to shuffle.

As I finished the interview, Megan mentioned that she was about a month pregnant. My heart immediately sank. Pregnancy would limit both diagnostic and therapeutic options. The course of her disease, whatever it might be, could also affect the baby.

First things first, I reminded myself. I could worry about the pregnancy later. I noticed that throughout the examination, Megan smiled like a Cheshire cat. It looked like a forced grin, known as risus sardonicus. Although her neurological responses were normal, I noticed a small, irregular tremor in her head and hands, both when she was standing and lying down. When I tested her coordination, her movements weren't as brisk as I would have expected for a 22-year-old. The only other abnormality I found was a slight tendency to take small and hesitant steps when she walked.

My mind raced with the diagnostic possibilities. Parkinson's? But she was so young, too young. Drugs? Toxins? Medication? The screen for drugs in her urine was negative, she denied any known toxin exposures, and she wasn't taking any medication. An alphabet soup of neurodegenerative disorders came to mind—hellish, invariably fatal diseases—but Megan didn't fit the profile for any of them. There is a benign form of tremor that runs in families, but Megan's symptoms were too complex for that condition. I couldn't dispel the nagging thought that this might be something metabolic—something biologically simple yet sinister in its presentation.

I stalled for time. My head ached and the blood pounded in my temples as I ran over the possibilities. Megan waited patiently, her eyes full of anticipation. I finally recalled a conversation I'd had many years ago with my mentor. In a young patient with a tremor, especially a patient with a history of psychiatric illness, remember copper, he had said. Think Wilson's disease.

Suddenly the psychiatric symptoms, the tremor, and the shuffling gait made sense. Megan had a disease that would explain both her tremor and her mental illness.

Copper is an essential trace element, and most diets provide about one-quarter more than is needed for cellular metabolism. The liver processes this excess copper into bile, which is excreted in the stool. Some people inherit a defect in this processing pathway, and symptoms occur as harmful amounts of copper accumulate in the brain and the liver. One visible sign of copper deposition is greenish-brown rings around the cornea, called Kayser-Fleischer rings.

The defect has been traced to a gene on chromosome 13, and about 200 variations of the mutation have been documented. People carrying only one affected gene may have mild symptoms or none at all. For that reason, most patients with Wilson's disease have no family history of the condition. A child must inherit the altered gene for copper metabolism from both parents in order to develop the disease.

Wilson's disease occurs in about 1 in 30,000 people and usually begins between the ages of 10 and 40. Symptoms vary and include hepatitis, liver damage, tremor, slurred speech, lack of coordination, cramping, emotionality, depression, parkinsonism, psychosis, and other bizarre behaviors. The sheer diversity of clinical manifestations often hinders early recognition, just as it had in Megan's case.

Once the disease is suspected, however, confirming the diagnosis is not difficult. In many patients a blood analysis detects a low level of the copper-binding protein ceruloplasmin. A 24-hour urine sample shows elevated levels of copper in all untreated and symptomatic patients. A careful eye exam reveals Kayser-Fleischer rings, and if necessary, a biopsy can document elevated copper levels in the liver.

A quick and accurate diagnosis is imperative because if treatment is begun early, symptoms can dramatically improve. When patients are first diagnosed, they are given an agent that will chelate, or bind, copper. After binding to the copper, the agent is eliminated. The follow-up treatment is lifelong therapy with zinc, which effectively blocks the absorption of copper in the intestine.

Although I evaluated Megan quickly, it took a few weeks to get the results of her blood tests. When they finally arrived, the numbers were not surprising: Her urinary copper was very high, and her serum ceruloplasmin was low, but thankfully her liver function tests were normal. An ophthalmology evaluation found dramatic Kayser-Fleischer rings around Megan's corneas. But in the meantime, her condition had deteriorated: Her walk had become unsteady, and her anxiety had increased.

I wanted to treat her aggressively, but her pregnancy weighed on my mind. I discussed her case with several other specialists, and we agreed that treatment with a chelating agent should not pose an undue risk to the baby. Megan began taking the chelator. At the same time, she also began zinc therapy, which takes several months to have an effect.

The treatment didn't go as smoothly as I would have hoped. Megan frequently forgot doses of her medication and often didn't get to the lab in time for her monthly urine samples. But as the weeks passed, her condition did stabilize. After a few months, as the chelation progressed and her copper burden decreased, I began to see a definite improvement. The tremor all but disappeared, and the graceful elegance of her walk had nearly returned.

Best of all, a series of ultrasounds revealed no obvious problems with her baby. Although the child would inherit one of Megan's abnormal genes, early screening would allow for swift treatment should any symptoms develop.

I found out about the birth of Megan's baby some time after she had delivered. One day she simply called the office for a prescription refill. She casually mentioned to my medical assistant that she and the baby were both fine, thanks, and without missing a beat, asked when she could stop by to pick up the prescription.

I still closely monitor Megan's condition, and both she and the baby continue to do well. She recently stopped by to pick up a note for work, and after we chatted for a few minutes, she asked me if I'd like to hold her child. As I rocked that beautiful baby in my arms, it occurred to me that for the moment, at least, I no longer had to worry.