Project by Hailey Russell

What is Huntington’s Disease (HD)? A point mutation that is autosomal dominant Caused by a genetic defect on chromosome 4 This defect causes a part of DNA, a CAG

repeat, to occur many more times than is needed

Normally it is repeated 10-35 times, but in people with HD, it is repeated 36-120 times

As the gene is passed through generations, the number of CAG repeats get larger and larger

How is it inherited? Because the affected allele is dominant, only

one parent has to be homozygous dominant or heterozygous to possibly give the child HD

If the parent is homozygous recessive, the parent neither has nor can give the child the disease

Since only 1 allele is passed, the child has a 50% chance of inheriting the affected allele from the diseased parent

2 diseased parents: 75% chance of child receiving allele (50% dominant disease, 25% double dominant)

HD Pedigree

Are There Other Ways of Getting HD? 3% of HD cases have been sporadic These instances can occur when a child

has HD even though there is no other family history of the disease

They are caused by a new genetic mutationOrigin of mutation is always paternalThis is an alteration in a HD gene that

occurs during sperm development

What are the Symptoms? Movement Symptoms

Chorea (involuntary, rapid, ceaseless movement)○ Can become more intense when the person is

anxious or disturbedClumsinessJaw clenchingLoss of coordination/balanceSlurred speechDifficulty swallowing/eatingUncontrolled continual muscular contractionsDifficulty walking/stumbling/falling

Cognitive SymptomsOvertime dementia

developsAbility to concentrate

becomes more difficultPerson may have trouble

driving, keeping track of thins, answering questions, and making decisions

Can possibly lose ability to recognize familiar objects

Psychiatric SymptomsDepression

○ Most common and develops early in course of disease

○ Signs include: hostility/irritability, inability to take pleasure in life, lack of energy

DelusionsHallucinationsInappropriate behavior

○ i.e.: unprovoked aggressionParanoiaBipolar disorder

How Does HD Affect Individuals?

Usually signs of disease are revealed during middle age (between 30 and 45)

When the signs of the disease appear may vary

Symptoms progressively get worse and worse

The earlier the symptoms appear, the faster the disease progresses

Usually die within 15 to 20 years Cause is often because of infection,

but cases of suicide are also common

How Many Affected Individuals are There? Worldwide, there are about

5-10 cases per 100,000 people

Around 30,000 people in North America have the disease

Another 150,000 people in North America are considered “at risk” for inheriting the illness because they have (or had) a parent with HD

Who is More Likely to Get HD? The disease affects women and men

equally All ethnic groups can be affected Rate of occurrence is higher in Western

European descent though, averaging around 70 per 1 million people

In people with African or Asian decent, the rate is 1 in a million people

What is the Incidence of Carriers? 0% HD and other

autosomal dominant diseases do not have carriers

If a child receives the diseased allele, the child is automatically infected with HD

Are There Treatments? No cures or ways to stop the disease

from getting worse are known The goal of the treatments is to slow the

course of the HD and help the affected individual to function for as long and comfortably as possible

Dopamine blockers: help reduce abnormal behaviors

Tetrabenazine/amantadine: try to control extra movements

Is There Hope? Huntington’s Disease

Society of America Organization dedicated

to improving the lives of people with HD

Promote and support research of HD

Help people and families cope with the struggles brought by the disease

Educate the public and heath professionals about HD

Bibliography

eMedTV. (November 30, 2006). Inheriting Huntington’s Disease. Retrieved from http://nervous-system.emedtv.com/huntington's-disease/inheriting-huntington's-disease.html. May 19, 2011.  

HealthCommunities.com. (May 19, 2011). Signs & Symptoms of Huntington’s Disease, Complications. Retrieved from http://www.healthcommunities.com/huntingtons-disease/symptoms.shtml. May 13, 2011.

Huntington Study Group. (2010). A Huntington’s Disease Overview. Retrieved from http://www.huntington-study-group.org/HDBasics/tabid/91/Default.aspx. May 20, 2011.

Huntington’s Disease Society of America. (2008). HDSA Mission. http://www.hdsa.org/about/our-mission.html. May 21, 2011.

  MedlinePlus. (May 2, 2011). Huntington’s Disease. Retrieved

from http://www.nlm.nih.gov/medlineplus/ency/article/000770.htm. May 12, 2011.

New York Times. (May 22, 2007). Huntington’s Disease. Retrieved from http://health.nytimes.com/health/guides/disease/huntingtons-disease/overview.html. May 18, 2011.

  Wrong Diagnosis. (April 29, 2011). Inheritance and Genetics of

Huntington’s Disease. Retrieved from http://www.wrongdiagnosis.com/h/huntingtons_disease/inherit.htm. May 20, 2011.