On Wednesday I challenged readers to figure out a fascinating case of a 52-year-old father of two disabled sons who experienced sudden weakness in his legs, low potassium and hyperthyroidism. More than 220 of you shared your thoughts and, astonishingly, 61 correctly diagnosed this patient.
I suspect that some of you used the same strategy to put it all together as the doctor who ultimately helped solve the real case.
The correct diagnosis is …
Thyrotoxic periodic paralysis (also called hyperthyroid hypokalemic periodic paralysis)
The first correct answer came from Aaron Milestone of Brooklyn, less than an hour after the story was posted. Mr. Milestone, 37, is a graphic designer and volunteer emergency medical technician (E.M.T.) who is studying to go to medical school. He tells me that he once saw a documentary about a boy with a genetic condition called hypokalemic periodic paralysis and used Google to find a connection with that illness and hyperthyroidism.
A number of other readers came close to the right answer by guessing hypokalemic periodic paralysis, but they didn’t take the next step and link the condition to the patient’s hyperthyroidism.
How the Diagnosis Was Made:
After the patient was admitted to the intensive care unit, Dr. Kathleen Samuels, a second year resident, presented the case to a roomful of colleagues and teachers in the daily conference known as Resident Report.
As the residents hashed out the case, Dr. Jeremy Schwartz, one of the chief residents, thought of hypokalemic (from the Latin, meaning low potassium) periodic paralysis, a genetic disease that causes a transient paralysis similar to what the patient had. However, this type of periodic paralysis usually shows up much earlier, when patients are in their teens, and frequently develops into a slowly progressive muscle wasting disease in late middle age.
Dr. Schwartz wondered whether there could be a form of this disease that showed up later in life and was not inherited. Could the periodic paralysis be linked to the man’s hyperthyroid state? Or even his diabetes?
As the discussion carried on around him in the conference room, Dr. Schwartz checked a medical reference site on the computer and searched for a paper describing a disease that combined hypokalemic periodic paralysis and hyperthyroidism. As soon as he hit the enter key, page after page appeared, filled with articles describing an acquired version of hypokalemic periodic paralysis triggered by high levels of thyroid hormone.
The Diagnosis:
In the inherited version of hypokalemic periodic paralysis, young men (mostly) are born with cells that have a tendency to suck up potassium under the right circumstances. These attacks usually come on after a high carbohydrate meal, after intense exercise or during times of stress — conditions that can trigger the release of insulin. The insulin, in turn, tells the cells to suck up potassium. Too much thyroid hormone also signals cells to take up potassium. This can result in dangerously low levels of potassium in the fluid outside the cell where it’s needed for muscles to work.
This patient had it all. Blood tests showed that he had high levels of thyroid hormone, glucose and insulin. In addition, he was experiencing high levels of stress because his oldest son was in the hospital. After the diagnosis, he told the resident that for the past few weeks he’d also been living on high-carbohydrate foods from hospital vending machines.
Still, hyperthyroidism is common; diabetes is common; high carbohydrate diets and stress are epidemic; and yet this kind of periodic paralysis is rare. Current thinking is that some patients have inherited a predisposition to develop thyrotoxic periodic paralysis under the right set of circumstances.
Notably, the condition is much more common in patients of Asian descent, a fact that Well blog readers frequently mentioned. But it can occur in patients like this one who are not Asian.
The Patient’s Story:
The patient was given a small dose of replacement potassium by mouth, and his potassium level returned to normal. The phosphate and magnesium also improved without any additional treatment, and his strength returned as his blood chemistry normalized. Thyroid tests revealed that the patient had Grave’s disease, a disorder in which the immune system somehow triggers the thyroid to overproduce its normally tightly regulated hormone. The patient was started on a thyroid medication, and since his thyroid has been under control, he hasn’t had another attack of pain or weakness for the past five months.
I learned about this patient because I was his doctor of record. I last saw him two years ago in my clinic. He came to me because he had heartburn, but I had noted his rapid heart rate and tremor and suspected that he had hyperthyroidism. I gave him a lab slip to check his thyroid hormone, but he didn’t follow through and get his blood drawn. He didn’t come to see me again until after he was discharged from the hospital.
I reminded him of our earlier appointment. Why hadn’t he gotten the blood test I ordered for him? Why hadn’t he come back? He looked a little embarrassed, but his answer was direct: his complaint had been the heartburn, and the pill I prescribed fixed that. My concerns about hyperthyroidism didn’t seem important to him. He didn’t care about a body part he’d never heard of, possibly causing a disease with symptoms he didn’t feel. Indeed, like many people with overactive thyroids, he felt great.
All that changed when he lost his strength. Suddenly, he told me, he was quite literally unable to care for his two disabled 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 told me. “I have to take care of myself so I can take care of my kids.”
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