The Physiology of a Neurodegenerative Disease by Christine M. Fleet

Part I—Symptoms of Huntington’s Disease

Amanda is in her second year of graduate school. While working in the lab one afternoon, she receives a worrisome call from her parents. Her uncle Gerald has just been diagnosed with Huntington’s disease (referred to as “HD”) and Amanda’s parents are trying to make sense of the diagnosis and figure out how to help.

There is only time for a brief conversation on the phone, but the diagnosis leaves Amanda very concerned. Her uncle lived nearby when Amanda was a child and often joined the family for dinners. He was an important part of the family and it was shocking to hear the diagnosis. What would it mean for her uncle, and what would she and her family be able to do to help him?

Amanda is the first in her family to pursue an advanced degree and the only scientist, so she knows that her parents will be looking to her to help them understand the diagnosis and consider a plan of action. As a genetics student, she knows that HD is inherited as a single-gene, autosomal dominant trait. In fact, it’s a classic example of human genetic disease. Amanda remembers hearing that it usually strikes during middle age and causes neurodegeneration, but she can’t recall much else about it. After attending the required research seminar for graduate students in biology departments at the university medical center, she catches up with a couple of fellow students, hoping they can help her better understand Uncle Gerald’s diagnosis—Steven, a neurobiology student, and Michelle, an MD/PhD student. When Amanda tells them about Uncle Gerald’s diagnosis, both friends express their sympathy.

“That’s a pretty awful disease,” Steven says. “Had anyone noticed any symptoms leading up to it?”

“Not really. Uncle Gerald works for a printing company. He’s done pretty well with the business, but ever since he turned 40 a couple of years ago, some of the folks at the print shop said he was starting to be a bit of an eccentric—odd facial expressions, twitchy sometimes, a little harder to get along with. I guess he had a pretty bad fall last week—broke his leg. The doctor must have started putting the pieces together when he took the family history. But up until a few years ago, Uncle Gerald was always really easy to get along with, a pretty normal guy. I know the doctor suspects a neurodegenerative disease, and you can identify Huntington’s with a genetic test, but how is this disease different from other cases of neurodegeneration, like Parkinson’s or Alzheimer’s?”

Question

1. 1. What are the classic symptoms of HD, and how are these similar to and different from symptoms of Parkinson’s or Alzheimer’s?

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