House of Mind

"Biology gives you a brain. Life turns it into a mind" - Jeffrey Eugenides

  • 28th June
    2011
  • 28
I just read your reblog about Huntington's and I was wondering... is adult onset Huntington’s just suddenly triggered at a certain age (with the approrpriate number of repeats in their genome since birth) or are the repeated segments repeated in replication errors until the number of tandem repeats triggers the disease?

Asked by: cassjamminx

Hey, 

Great question! I’ve been searching online and can’t arrive at a solid answer. I personally don’t know, but from what I’ve read I think it’s the number of tandem repeats that triggers the disease… For example, people with +40 tandem repeats usually develop the disease while people with 36-40 repeats may or may not develop the disease.

Here’s the link I found useful: http://ghr.nlm.nih.gov/condition/huntington-disease

  • 24th June
    2011
  • 24
Daily Diseases and Disorders: Huntington's Disease

dailydiseasesanddisorders:

Huntington’s disease is a neurodegenerative genetic disorder that greatly affects muscle coordination and cognition. The nerve cells in the brain slowly breakdown and atrophy. Huntington’s disease affects the striatum of the brain as well as the hippocampus, purkinje cells, and the cerebellum. 

Huntington’s is an autosomal dominant genetic disease that results from a defect on chromosome #4. The defect causes a repeat in a CAG sequence on the DNA to occur many more times than normal. In person without Huntington’s, the CAG sequence is repeated 10 to 35 times. In an individual with Huntington’s disease, the repeat can be repeated 36-120 times. The repeated sequence is expanded as it is passed through one generation to the next, lengthening the sequence in each offspring. Therefore, the disease becomes progressively juvenile. If one parent has Huntington’s, the child has a 50% chance of having the disease as well. 

There are two types of Huntington’s: juvenile which appears in children and the much more common form, adult-onset Huntington’s which appears in an individual aged 30 to 40. 

Huntington’s disease has become a target due to the ethical issues associated with it. Many question when an individual should be tested for the disease, if at all. Preimplantation genetic diagnosis has been used as a selective form of abortion. Some individuals who might have the disease may opt to not have the disease diagnosed. 

Worldwide, 5-10 people out of 100,000 have the disease.

After the first onset of symptoms, an individual typically has a life span of twenty more years of life. Huntington’s has no cure and ultimately leads to death. Suicide is one of the greatest cause of fatalies in the disease with 7.3% with Huntington’s taking their own lives and up to 27% attempting suicide. 

Diagnosis: A genetic counselor can determine if the child will have Huntington’s disease using genetic testing. The geneticist will look at the number of CAG repeats and determine the likelihood of the person developing Huntington’s in their life. In most cases, the affected individual will have an idea of when the symptoms will onset. A physical diagnosis that analyzes the symptoms of Huntington’s is also effective for most patients. Medical imaging of the brain can also show which areas of the brain have atrophied. 

Symptoms: Huntington’s disease affects many parts of the body. Movement disorders can include involuntary jerking, sustained contraction of muscles, rigidity, diffulty with speech, posture problems, and difficulty swallowing. Cognitive disorders include difficulty with organization, emotional flexibility, lack of focus and reasonable thinking, and various other symptoms. Lastly, psychiatric disorders include sadness, unhappiness, social withdrawal, loss of interest, fatigue, feelings of guilt, reduced appetite, and reduced sex drive.

Treatment: There is no cure for Huntington’s disease. Some of the symptoms can be controlled with various antidepressants and other drugs that reduce the amount of involuntary muscle jerking. 

Additional Information: Huntington’s disease has become prominent in different media sources and has appeared in Everwood, House, Private Practice, ER, and Scrubs. 

  • 19th January
    2011
  • 19
neurolove: Basal Ganglia Disorders Let’s go back to the basal ganglia, where I had left off in the past. The basal ganglia are pretty important, smoothing and promoting/inhibiting thoughts, feelings, and movements.  We usually think of them in terms of movement since that is the most obvious and simplest use of the basal ganglia circuitry.  There are two main disorders that are directly linked to basal ganglia function- Parkinson’s Disease and Huntington’s Disease.  Parkinson’s affects the dopamine neurons along the nigrostriatal pathway (neurons going from the substantia nigra- “nigro”- to the striatum- “striatal”) that feed into the basal ganglia (at the striatum) to promote movement (thus why PD is decreased movement), while Huntington’s involves the breakdown of cells in the inhibitory indirect basal ganglia loop (in the striatum), causing extra movements.  I’ll talk more about each of these in the next few days. [Image Source]

neurolove:

Basal Ganglia Disorders

Let’s go back to the basal ganglia, where I had left off in the past. The basal ganglia are pretty important, smoothing and promoting/inhibiting thoughts, feelings, and movements.  We usually think of them in terms of movement since that is the most obvious and simplest use of the basal ganglia circuitry. 

There are two main disorders that are directly linked to basal ganglia function- Parkinson’s Disease and Huntington’s Disease.  Parkinson’s affects the dopamine neurons along the nigrostriatal pathway (neurons going from the substantia nigra- “nigro”- to the striatum- “striatal”) that feed into the basal ganglia (at the striatum) to promote movement (thus why PD is decreased movement), while Huntington’s involves the breakdown of cells in the inhibitory indirect basal ganglia loop (in the striatum), causing extra movements.  I’ll talk more about each of these in the next few days.

[Image Source]