"Can you help me?" The 52-year-old father called out to his son, who was asleep in the other bedroom. It was nearly midnight, and the man, awakened from sleep, tried to get up to go to the bathroom. When he stood, he was surprised to find that his legs had no strength, and he fell. Now he needed help to get back up. His son, 21 and mentally disabled, came into the room. His father quietly talked him through what he had to do to get him onto the bed. Then he picked up the phone and called a friend to come stay with his son. Once that was arranged, he dialed 911.
1. IN THE HOSPITAL
Dr. Kathleen Samuels, the resident admitting patients to the intensive care unit that night at Waterbury Hospital in Connecticut, had already admitted several by the time she got the call about the man who couldn't walk. He had a life-threateningly low level of potassium in his blood. Potassium is an essential electrolyte, and the body normally holds it at a constant level. The E.R. doctor hadn't figured out why this man's potassium was so low, but he was certain he needed to be monitored in the intensive care unit until they understood what was going on.
Samuels hurried to see the patient. He appeared healthy and seemed surprised that he couldn't walk. He told her that he was well until two days earlier, when he started having pain in his hips and knees. The pain was constant but was worst in the morning and when he walked. He went to the emergency room twice in those two days. The first time, he left after a few hours. He hadn't seen a doctor, but he had to pick up his son from his day care program. He came back the next day, and the E.R. doctor told him it was arthritis and prescribed a painkiller. He didn't get a chance to pick up the medicine, and now he couldn't walk. He had no other medical problems, and he took no medicines. He didn't smoke or drink, and he took care of his two disabled adult children — one of whom had been in the hospital for the past two weeks.
2. THE DOCTOR'S EXAM
The patient could lift his legs off the bed, but he wasn't able to keep them up if Samuels applied even a little pressure. He had a slight tremor, but the patient told her that he'd had that for years. Otherwise the exam was unremarkable. His labs, on the other hand, were anything but. Not only was his potassium low but so too were his white blood cell count and platelets. His blood sugar was high and so was his thyroid hormone. The thyroid gland tells the body how hard to work, and this thyroid was telling the body to work very hard indeed. But it was only the very low potassium that could kill the man, and that's what commanded Samuels's attention. She made sure that he was given enough potassium to replace what he'd lost and then tried to figure out why he lost it.
3. POSSIBLE DIAGNOSES
Diarrhea and vomiting are common causes of low potassium. This patient said he had neither.
Potassium is regulated by the kidneys. Although his kidneys appeared normal, he would need more extensive testing.
Some medications cause the kidneys to dump excessive amounts of potassium into the urine, but this patient took no medications.
4. RESIDENT REPORT
At 7:30 that morning, Samuels went to the hospital's Resident Report, a daily meeting for physicians in training, where much of the teaching on diagnostic thinking takes place. Residents and teaching physicians gather in a conference room to think through the process of making a diagnosis for a patient admitted to the hospital. This morning Samuels laid out the case of the man who couldn't walk — how the patient looked, what she found during the exam and what his lab results revealed.
As the doctors hashed out the case, Dr. Jeremy Schwartz, one of the chief residents, remembered something. This patient's symptoms sounded just like an illness he'd read about: a genetic disorder called hypokalemic periodic paralysis. "Hypo" from the Greek meaning low and "kalium" from the Latin meaning potassium. In this disease, patients experience transient episodes of severe weakness caused by low potassium. But there was one big difference — this inherited disease is usually first seen in adolescence. This man was much too old to be having his first attack. Could there be a form of the disease that was acquired and not inborn? Could it be linked to something else the man had — to his high thyroid or sugar?
Schwartz was sitting next to the computer in the conference room. He went to a medical reference site and typed in hypokalemic periodic paralysis and hyperthyroidism. As soon as he hit enter, page after page appeared, filled with articles on a disease known as thyrotoxic periodic paralysis.
5. HOW IT WORKS
In the inherited version of hypokalemic periodic paralysis, young men (mostly) are born with cells that can suck up potassium after a high-carbohydrate meal, after exercise, upon awakening from sleep or during times of intense stress. Patients with this genetic disorder can reduce their risk of paralytic attacks by taking medicines that increase the amount of potassium in the blood and by eating a low-carbohydrate diet.
This man didn't have this genetic disease, but having too much thyroid hormone made his body act as if he did. When high levels of thyroid combine with high blood sugar, a high-carbohydrate diet or high stress, cells can take up so much potassium that there's just not enough outside the cell, where it's needed for muscles to work. This patient had it all. Blood tests revealed that he had high levels of thyroid hormone and high blood sugar. He was experiencing high levels of stress because his older son was in the hospital, and in addition, he was living on high-carbohydrate foods from the vending machines there.
Still, hyperthyroidism is common; high blood sugar is common; high-carbohydrate diets and stress are epidemic; and yet this kind of periodic paralysis is rare. Current thinking is that these patients also have a genetic abnormality that predisposes them to develop periodic paralysis if and when they ever develop hyperthyroidism.
The patient was given a small dose of replacement potassium by mouth, and his potassium and his strength returned to normal. The patient was started on a thyroid medication, which alleviated the pain and weakness.
I heard about this patient because I was his primary-care doctor. I last saw him two years before this episode when he made an appointment because he had heartburn. I gave him a medication for the heartburn, but I also noticed that he had a rapid heart rate and a tremor, and I suspected that he had hyperthyroidism. I gave him a lab slip to check his thyroid hormone. He never went.
When I saw him after he was discharged from the hospital, I asked why he had never gotten the blood test. He looked a little embarrassed, but his answer was direct: his complaint had been the heartburn, and the pill I prescribed fixed that. Concerns about hyperthyroidism didn't seem important to him. He didn't care about a body part he had never heard of, possibly causing a disease with symptoms he didn't feel.
All that changed when he lost his strength. Suddenly, he told me, he was quite literally unable to care for his sons. "If I am not around, they will have no one," he told me. So now he takes his thyroid medicine regularly. He gets his blood drawn as often as needed to keep his disease in check.
"I don't do it for myself," he said. "I have to take care of myself so I can take care of my kids."