How Huntington's Disease Is Diagnosed

Huntington’s disease is diagnosed in several stages. You can have a genetic test to determine whether you carry the gene that causes the disease, and you would also have a clinical diagnosis when you develop symptoms. 

The condition is hereditary, and if one of your parents has Huntington’s disease, you have a 50% chance of inheriting the gene. Having the gene means that you will definitely eventually develop the condition.

The signs of Huntington’s disease can begin gradually—with personality changes, cognitive decline, involuntary movements, and diminished muscle control.

If you develop symptoms, you and your doctor would determine whether they are caused by Huntington’s disease or by something else. And then you can work together to plan treatment for managing your current symptoms, as well as creating a plan for managing future symptoms that are expected to emerge.

Huntington's disease is hereditary

Getty Images / Oliver Rossi

Self-Checks/At-Home Testing

Whether you anticipate developing Huntington’s disease in the future or whether you have already been diagnosed with the condition, you should be familiar with the effects of the disease so you can get medical attention if you develop them. 

Signs that you might have Huntington’s disease include:

  • Trouble with thinking and planning 
  • Worsening memory 
  • Mood changes 
  • Behavioral changes 
  • Diminished coordination, reduced ability to carry out specialized activities, or declining exercise or sports skills
  • Involuntary twitching or jerking of your muscles 

You can experience these effects intermittently, and they may increase in frequency. If you have a family history of Huntington’s disease and have had a positive genetic test, you can anticipate these issues starting in middle age or later.

If you have a family history of Huntington’s disease and have opted not to have a genetic test, these signs could indicate that Huntington’s disease is starting, or they can be an indication of another condition (such as depression). 

Advancing Disease 

If you have already been diagnosed with Huntington’s disease, your condition will likely decline.

Signs that your disease is worsening include:

  • Increasing frequency of involuntary movements 
  • Weakness or trouble controlling your movements 
  • Struggling to walk, or falling down
  • Choking, or difficulty chewing and swallowing 
  • Severe depression or apathy
  • Difficulty with your speech
  • Fever (a sign of infection, which is a common complication)
  • Struggling to breathe 
  • Unstable behavior 

It’s important that you seek medical attention for worsening Huntington’s disease, because you could benefit from different interventions as your disease advances.

Physical Examination 

If you have signs of Huntington’s disease or if you know that you will develop the disease because you’ve had a positive genetic test, your doctor will look for early signs of the disease with a physical examination. This will include a detailed neurological and cognitive examination. 

Issues that can signal Huntington’s disease include:

  • Chorea: Tremors, twitches, writhing, or jerking movements. These might not necessarily occur while you are at your doctor’s appointment, even if they occur from time to time when you are at home.
  • Gait abnormality: You can have diminished strength or balance, and this can affect your ability to walk normally. 
  • Diminished coordination: You can have trouble controlling the purposeful movements of your arms and/or legs. 
  • Cognitive impairment: You may have difficulty concentrating, following directions, or recalling facts or events.
  • Depression: This can manifest with apathy (lack of interest or motivation) or a lack of expressiveness of emotion during your physical examination. 

The physical examination is not a definitive diagnostic feature of Huntington’s disease, but as the disease advances, detectable physical and cognitive abnormalities will emerge. Some of these abnormalities can be similar to those of other diseases, such as movement disorders or dementia—and these conditions might be considered during your diagnostic evaluation. 

Functional Scales 

After your diagnosis of Huntington’s disease, your medical team may track your condition using measures such as the Total Functional Capacity (TFC) scale or the Adult Functional Adaptive Behavior (AFAB) scale. These scales measure and score your cognitive and physical abilities.

The advantages of using these types of scales include objectivity and consistency. They can also serve as a way to assess milestones that might be used to help you decide when it’s time to make certain adjustments to your daily life (such as making the decision to stop driving or working). 

Labs and Tests 

The definitive test for Huntington’s disease is a genetic test that examines your DNA. This is done with a blood sample. This test can identify the presence of the genetic mutation (alteration) that causes Huntington’s disease.

The mutation is located on the HTT gene, which is found on chromosome four. If one of your copies of chromosome four has the mutation (which described as a CAG repeat) in the HTT gene, then you are expected to develop the condition. With Huntington’s disease, the CAG nucleotide pattern is repeated approximately 30 times.

Accuracy of the Genetic Test

If you have the gene mutation, you will develop the disease. And if you don’t have the gene mutation, you will not develop the disease. This test is considered highly accurate, with high sensitivity and specificity, and it is not associated with false positive or false negative results.

Besides the genetic test, there are no other biological markers that can indicate the presence or absence of Huntington’s disease, and there are no other tests that give any indication of the likelihood that you might or might not develop the condition at some time in the future.

Imaging 

Imaging tests are not considered a predictor or an indicator of Huntington’s disease. The condition is associated with atrophy (shrinking) throughout the brain, especially in the caudate and putamen areas, which are associated with cognitive and motor abilities. These changes are not consistent, however, and are not necessarily present in everyone who has Huntington’s disease. 

Many neurological illnesses are characterized by abnormalities that can be seen with brain imaging studies. Your doctor might order a brain magnetic resonance imaging (MRI) test or brain computerized tomography (CT) scan if other conditions are being considered as a cause of your symptoms. 

Furthermore, if you have been diagnosed with Huntington’s disease, you may need to have imaging tests to identify coexisting disease (such as a stroke) or complications of Huntington’s disease (such as head trauma due to falling). 

Differential Diagnosis 

A number of medical conditions can have symptoms similar to those of Huntington’s disease. Sometimes, these conditions can be differentiated from Huntington’s disease based on symptoms, physical examination, and diagnostic testing. But often, it’s the eventual progression over time that helps clarify the distinction.

Conditions that may be similar to Huntington’s disease include:

It is possible that you could have Huntington’s disease as well as another of these progressive neurological conditions, and the combination can lead to a confusing and difficult diagnostic process, with complex treatment planning.

A Word From Verywell

The diagnosis of Huntington’s disease involves a risk assessment, which is based on your family history and genetic testing. Confirmation that the condition has started to have its effects is based on your symptom history and your neurological and cognitive examination.

If you have the disease, you will also need to have periodic medical assessments to identify any decline that you might be experiencing as the disease progresses. 

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