Genetic Counseling in Huntington’s Disease: Questions Families Ask Around Testing

The envelope from the genetics clinic sat on the kitchen counter for eleven days. Inside was an appointment letter, nothing more, yet the woman who requested it kept moving it from the counter to the drawer and back again. Her mother had been diagnosed at 52. Her grandfather, everyone now realized, had probably had it too; the family had simply called him difficult. She was 31, planning a wedding, and she could not decide whether knowing would feel like freedom or a sentence.

That hesitation is not indecision. It is the appropriate weight of a decision that cannot be undone. The Huntington’s genetic counseling questions families bring to a first appointment are rarely about laboratory technique. They are about children, careers, siblings who do not want to know, and whether a number on a report should be allowed to reorganize a life.

This explainer walks through what counseling and testing actually involve, who is usually offered a predictive test, and what the days and weeks afterward tend to look like, using guideline-level evidence rather than family lore.

What does Huntington's genetic counseling actually involve?

Most people picture genetic counseling as a single appointment where someone draws blood and, a few weeks later, delivers a verdict. In Huntington’s disease it is closer to a guided conversation that unfolds across more than one visit, and the blood draw is optional. A genetic counselor is a health professional trained in medical genetics and in the psychology of decision-making around inherited conditions. Their role is not to steer you toward a test. It is to make certain that whatever you choose, you understand it fully first.

The first meeting usually covers your family history in detail, often drawn as a pedigree, a simple chart showing who in the family has been affected and how they are related. From there the counselor explains the biology: the HTT gene, the CAG repeat expansion, what a result would and would not reveal. Time is set aside for the questions that have nothing to do with chromosomes, such as how a result might change your relationship with a sibling, whether you would tell your employer, or how you would spend the evening after hearing the news.

Counseling does not end when a result is read. Follow-up sessions, sometimes alongside a neurologist, psychologist or social worker, are part of the standard approach described by the NIH National Institute of Neurological Disorders and Stroke and by the NHS. The concerns families raise tend to cluster into a handful of themes: inheritance, the meaning of the repeat number, who can be tested and when, family planning, privacy, and what living with the answer looks like. Each of those themes gets its own section below.

One point matters above all the others and deserves saying early. The pace is yours. A good counseling service will let you pause between sessions, come back after months, or walk away entirely without ever giving a sample.

How does the Huntington's disease inheritance pattern work?

Huntington’s disease follows an autosomal dominant inheritance pattern. Autosomal means the gene sits on one of the numbered chromosomes rather than the X or Y, so it affects all sexes equally. Dominant means a single altered copy is enough; you do not need to inherit a change from both parents. The gene is called HTT and it sits on chromosome 4, according to MedlinePlus Genetics.

Each child of a parent who carries the expansion has a 50 percent chance of inheriting it, and a 50 percent chance of not inheriting it. That figure resets with every pregnancy, in the same way a coin does not remember its last toss. Three siblings can all inherit the expansion, or none can. If you did not inherit it, the line stops with you: your children cannot inherit what you do not carry.

The condition is uncommon. MedlinePlus Genetics puts the prevalence at roughly 3 to 7 per 100,000 people of European ancestry, with lower reported rates in some other populations. Adult-onset Huntington’s, the most common form, usually shows its first signs in a person’s thirties or forties. A juvenile form that begins in childhood or adolescence is far less common.

New cases without a known family history do happen, though rarely. They can arise when a parent carried an intermediate repeat number, high enough to expand further when passed on but not high enough to cause symptoms in the parent, or when a parent died young of another cause before signs appeared. This is one reason counselors take such care over the family tree. A grandparent’s early death, a relative labeled with a psychiatric diagnosis, or a great-uncle nobody talked about can turn out to be part of the pattern.

What does the CAG repeat number in a Huntington's test mean?

The Huntington’s test counts how many times a three-letter DNA sequence, cytosine-adenine-guanine, written CAG, repeats within the HTT gene. Everyone has some repeats; the question is how many. The laboratory reports a number for each of your two copies of the gene, and counselors interpret the higher one.

CAG repeats	Usual interpretation (MedlinePlus Genetics)	Relevance for children
26 or fewer	Normal range; not associated with Huntington’s	No expansion to pass on
27 to 35	Intermediate; the person is not expected to develop symptoms	Repeat may enlarge when passed on, so a child could be at risk
36 to 39	Reduced penetrance; may or may not develop symptoms in a normal lifespan	Each child has a 50 percent chance of inheriting the repeat
40 or more	Full penetrance; almost always develops symptoms	Each child has a 50 percent chance of inheriting the repeat

The middle rows are where interpretation gets delicate. A result of 36 to 39 repeats is described as reduced penetrance: some people with these numbers develop symptoms, some never do, and the test cannot say which group you belong to. An intermediate result of 27 to 35 is not expected to cause disease, yet the repeat can expand when passed to a child, especially through a father, because the sequence is less stable during sperm formation. MedlinePlus Genetics notes that larger repeats tend to appear at younger ages, a phenomenon called anticipation.

What the number does not do is set a date. Two people with identical repeat counts can develop symptoms decades apart, and factors beyond CAG length, some genetic and some not yet understood, influence timing. Counselors will tell you plainly that a positive result is a statement about probability across a lifetime, not a calendar. That distinction is worth holding onto, because it is the one people most often lose in the hours after hearing their result.

Who is predictive testing for Huntington's usually offered to, and who is asked to wait?

Predictive testing means testing a person who has no symptoms to learn whether they carry the expansion. It is usually offered to adults with a known family history who have completed pre-test counseling and who are asking for the test for their own reasons. That last clause is not a formality. Counselors routinely check whether a partner, parent or employer is applying pressure, because a result taken to satisfy someone else tends to be harder to live with.

Several groups are commonly asked to wait, or are guided toward a different route.

• People under 18. NIH guidance describes predictive testing as generally reserved for adults, since a minor cannot give fully informed consent to information that will follow them for life. The exception is when a doctor suspects juvenile Huntington’s based on symptoms, which becomes a diagnostic rather than predictive question.
• People in an acute crisis. Severe untreated depression, a recent bereavement or an unstable living situation are reasons to slow down, not to refuse. Counselors often suggest addressing the crisis first and returning when there is more capacity to absorb a result.
• People whose at-risk parent has not been tested. Testing here is possible, but it can reveal the parent’s status without their consent, so extra conversations are usual.
• People already showing possible symptoms. They are referred to a neurologist for a clinical assessment and, if appropriate, diagnostic testing, a process the Mayo Clinic describes as involving neurological, psychiatric and sometimes imaging evaluations alongside the gene test.

Being asked to wait is not a judgment about your maturity or your right to know. It reflects hard-won experience that the test is easier to carry when the ground beneath you is steady.

Huntington's genetic counseling questions about the testing appointments themselves

Families often want to know exactly what happens in the room. The sequence varies between services, but the shape is remarkably consistent across the protocols described by the NHS and NIH.

The pre-test phase is spread across more than one visit. You meet the counselor, review the family history, and go through the biology and the possible results. Many services also offer a baseline neurological examination, a brief check of movement, eye tracking and coordination performed by a neurologist, so that any future changes can be compared against a known starting point. Some include a meeting with a psychologist to talk through coping resources. None of this is a test you can fail. It is scaffolding.

If you decide to proceed, a blood sample is taken. The laboratory extracts DNA and measures the CAG repeat length on both copies of the HTT gene. You will be told roughly how long the analysis takes at your particular service; that interval is a laboratory turnaround, not a medical one, and it differs from place to place.

Results are given in person, by the counselor you already know, with a support person of your choosing present if you wish. Telephone or letter disclosure of a Huntington’s result is avoided in mainstream practice. You can decline to hear the result even at this stage, and some people do, asking that it be held on file until they are ready.

A follow-up appointment is scheduled regardless of the outcome, because a negative result can be surprisingly disorienting too. Bring a written list of questions to every visit. Bring the same person each time if you can. Counselors describe the appointments as a relay, not a sprint, and the people who fare best tend to treat them that way.

Predictive, diagnostic and prenatal testing: what is the difference?

The same laboratory measurement is used in three quite different clinical situations, and confusing them causes real misunderstanding.

Diagnostic testing is ordered when a person already has signs that could be Huntington’s: involuntary movements, changes in mood or thinking, difficulty with coordination. The Mayo Clinic describes it as one part of a wider workup that also includes a neurological history, a psychiatric evaluation and sometimes brain imaging. Here the gene test answers a present-tense question: is this illness Huntington’s or something else? It is arranged through a neurologist, though genetic counseling is still recommended because the answer has implications for relatives.

Predictive testing, covered in the previous sections, is for people without symptoms who want to know their status. It answers a future-tense question about lifetime risk and is surrounded by the fullest counseling process.

Prenatal testing examines a pregnancy. A sample of placental tissue or amniotic fluid is analyzed for the expansion. It raises a particular ethical tension that counselors will name directly: if the result is positive and the pregnancy continues, a child has effectively been tested as a minor, which mainstream practice otherwise avoids. Because of this, prenatal testing is usually discussed alongside the parents’ intentions before any procedure is scheduled.

A fourth approach, preimplantation genetic testing, sits before pregnancy. Embryos created through in vitro fertilization are tested and only those without the expansion are transferred. The Mayo Clinic lists it as an option to explore with a genetics specialist. It involves fertility treatment with its own demands, and no outcome can be promised.

Knowing which of these four you are actually being offered is the first thing to clarify at any appointment.

Huntington's prenatal testing and family planning: what are the options?

Few conversations in the counseling room carry more weight than this one, and few have more possible paths. Counselors lay them out without ranking them, because the right choice depends on values that belong to the family alone.

• Having children without any testing. Each child carries the same 50 percent chance described by MedlinePlus Genetics if a parent carries the expansion. Some families choose this path deliberately, reasoning that decades of healthy life, and the possibility of future treatments, are worth the risk.
• Prenatal diagnostic testing. Discussed in the previous section, this tells you whether the pregnancy carries the expansion.
• Exclusion testing. This clever variant is designed for an at-risk parent who does not want to learn their own status. Rather than looking for the expansion directly, the laboratory checks which grandparent’s copy of chromosome 4 the pregnancy inherited. If it came from the unaffected grandparent, the pregnancy is not at risk. If it came from the affected grandparent, the pregnancy carries the same 50 percent risk as the parent, without revealing whether the parent actually has the expansion.
• Preimplantation genetic testing with IVF. Embryos are tested before transfer. This can also be done in an exclusion format for parents who do not want their own result.
• Donor eggs or sperm, adoption, or choosing not to have children.

Fertility treatment adds physical, emotional and practical demands, and counselors are careful not to present it as a guaranteed route to an unaffected child. Timing matters too: prenatal options have windows in pregnancy, and preimplantation testing requires planning well before conception. Raising these questions early, ideally before a pregnancy is underway, gives a couple the widest set of choices and the least pressure.

What are the downsides of knowing, and the upsides?

A genetic result is one of the few pieces of medical information you cannot unlearn. Counselors ask people to picture both outcomes in concrete detail before proceeding, and the exercise is revealing.

A positive result brings certainty about something that cannot currently be prevented. Mayo Clinic and NIH sources are explicit that available treatments manage symptoms but do not stop or reverse the underlying process. For some people that makes the knowledge feel heavy: they describe watching themselves for every dropped cup or forgotten name. Relationships shift. A partner may grieve prematurely; a parent may feel responsible. Practical consequences follow too, discussed in the next section.

A negative result is not the pure relief people expect. Counselors regularly see something like survivor guilt, especially when a sibling has tested positive. Some people have organized their whole adult life around an assumption of illness, declining promotions or delaying children, and a negative result can trigger a disorienting question: what now?

The upsides are real and specific. A result ends the uncertainty that some find harder than any answer. It allows informed decisions about children, finances, career and where to live. It can open the door to research participation, since many observational studies enroll people who know their status. And for those who test negative, it lifts the risk from their children entirely.

Research summarized by the NIH suggests that most people who complete a structured counseling process adjust over time to either result, though the path is rarely smooth in the first months. The strongest predictor of coping well is not the result itself but the quality of support around the person receiving it. That is an argument for the counseling, not for or against the test.

Can a genetic test result affect my insurance or my job?

This is among the most practical Huntington’s genetic counseling questions, and it deserves a precise answer rather than reassurance.

In the United States, the Genetic Information Nondiscrimination Act, usually called GINA, prohibits health insurers from using genetic information, including predictive test results and family history, to decide eligibility or set premiums. It also bars employers with 15 or more employees from using genetic information in hiring, firing or promotion decisions, according to MedlinePlus Genetics.

The gaps matter as much as the protections. MedlinePlus is clear that GINA does not cover life insurance, disability insurance or long-term care insurance. Insurers offering those products can ask about genetic test results and family history, and can act on the answers. GINA also does not apply once a person has symptoms, because at that point the condition is a diagnosis rather than a genetic predisposition. Members of the military and some other groups fall under separate rules.

Counselors therefore raise a sequence of practical questions before testing. Do you want to review your life or disability coverage first? Would you prefer the result kept in a separate genetics record rather than your general medical chart, where services allow it? Who in your workplace, if anyone, needs to know? None of this is legal advice, and a counselor will say so; for complex situations they may suggest speaking with someone who specializes in disability or insurance law.

Outside the United States, protections vary widely, and some countries have moratoria or codes under which insurers agree not to ask about predictive results below certain policy values. If you live or work across borders, say so at the first appointment so the counselor can point you to the right information for your situation.

What do the days and weeks after a result usually look like?

People often prepare intensively for the appointment and hardly at all for the drive home. Counselors encourage the opposite balance.

The first few days after either result are frequently described as numb rather than dramatic. Many people report that the information does not feel real until something ordinary happens: filling out a form that asks about family history, or catching a glimpse of a parent’s gait in their own reflection. Services generally advise clearing the day of the result and, where possible, the day after. Having someone else drive is a small kindness that turns out to matter.

A follow-up counseling appointment is standard within the weeks that follow, and further sessions are available on request. NIH and NHS guidance both describe ongoing support, including referral to a psychologist or a Huntington’s specialist clinic, as part of the process rather than an add-on. For those with a positive result, this is also when a plan for periodic neurological review is discussed. Such reviews are not about waiting for symptoms; they establish a baseline and connect you to a team before you need one.

The weeks after a negative result deserve just as much attention. Some people book the follow-up and then cancel it, feeling they have no right to take up time. Counselors push back gently on that. Adjusting to good news that arrives after years of dread is legitimate work.

Telling relatives is usually the next milestone, and it is rarely a single conversation. Some people share within hours; others wait months. There is no correct timetable. The one thing counselors consistently recommend is to decide in advance who will hear it from you directly, so that no one learns through a group message or a grieving sibling.

How do I talk to relatives, and what if my parent has never been tested?

A Huntington’s result is never purely individual. The same expansion that appears in your blood came from a parent and may sit in siblings, cousins and children. That shared biology creates conversations that ordinary medicine rarely forces.

The untested parent is the classic dilemma. Imagine a 28-year-old whose grandmother had Huntington’s and whose father, now 55, has chosen never to test. If she tests positive, her father almost certainly carries the expansion too; the information has been revealed without his consent. Counselors do not refuse to test in this situation, but they will explore it thoroughly. Some families resolve it by talking openly beforehand. Some adult children proceed and keep the result private from the parent. Some parents, once they understand their child’s wish to know, decide to test themselves first. There is no protocol that removes the tension; there is only honest conversation about it.

Siblings present a mirror-image problem. A negative result in one sibling can feel like an accusation to another who tested positive, or an unwelcome nudge to one who has chosen not to test. Cleveland Clinic and NHS resources both emphasize that each relative’s decision about testing is their own, and counselors are careful never to contact family members on a patient’s behalf without explicit permission.

Children raise the question of when and how much to say. Most guidance favors age-appropriate honesty in stages rather than a single revelation, and many services offer family sessions for exactly this purpose. A child who grows up knowing that Huntington’s is part of the family story, and that there are adults calmly managing it, tends to reach 18 better equipped to make their own testing decision than one who discovers it by accident.

Is choosing not to test a reasonable decision?

Yes, and it is worth saying so without hedging. Across the countries that have offered predictive testing for Huntington’s since the gene was identified, most at-risk adults have chosen not to be tested. That is not a failure of education or a sign of denial. It reflects a considered judgment that, for many people, living with a 50 percent risk is preferable to living with certainty in either direction.

The reasoning people give is coherent. No treatment currently changes the course of the underlying disease, as the Mayo Clinic and NIH note, so a positive result does not unlock a preventive therapy. Insurance protections have gaps. A result affects relatives who did not ask for it. And some people simply want to live the years they have without a number attached.

Choosing not to test does not mean choosing to do nothing. Counseling remains available; many people attend precisely to work through the decision and then step away. Exclusion testing and exclusion preimplantation testing exist so that family planning can proceed without the parent learning their own status. Practical steps such as reviewing insurance, keeping general health strong and knowing which neurologist to call if symptoms ever appear are open to everyone at risk, tested or not.

The decision can also change. Someone who declined at 25 may return at 40 when planning retirement, or when a treatment trial becomes relevant. Counselors describe the door as staying open in both directions. What they discourage is deciding under pressure, whether from a relative who wants to know, a partner who is frightened, or an internal sense that a responsible person ought to find out. Responsibility here means understanding the choice, not making a particular one.

What people often get wrong about Huntington's genetic testing

Years of family whispering create myths that no leaflet dislodges. These are the ones counselors correct most often.

Myth: if my parent has it, I will get it too. The risk is 50 percent for each child of an affected parent, according to MedlinePlus Genetics, not a certainty. Half of at-risk children do not inherit the expansion.

Myth: it skips generations. Huntington’s is dominant, so it does not hide in carriers who never develop it and then reappear. What looks like skipping is usually a relative who died of something else before symptoms began, or an intermediate repeat that expanded in the next generation.

Myth: the test tells you when symptoms will start. It reports a repeat number, which correlates loosely with age of onset across large groups but cannot predict an individual’s timeline. Two people with the same count can differ by decades.

Myth: only men pass it on. Both parents can transmit the expansion equally. The one sex-linked nuance is that repeats are more likely to enlarge when passed through a father, which is why juvenile cases more often have an affected father, as MedlinePlus notes.

Myth: symptoms that start late are milder. Age of onset and severity are separate matters, and the adult form follows a progressive course regardless of when it begins.

Myth: a positive result means you should stop planning a life. People with the expansion routinely spend decades without symptoms, raise families, build careers and participate in research that may shape future treatments. The result reorganizes some decisions. It does not cancel them.

Myth: genetic counseling is a hurdle designed to talk you out of testing. Its purpose is to make the decision, whichever way it goes, one you can stand behind.

Questions to ask your care team

Arriving with written questions changes the character of an appointment. It signals that you intend to be a participant, and it stops the important things from slipping away in the emotion of the moment. Consider adapting these.

• Which type of testing are you offering me: predictive, diagnostic, prenatal or preimplantation?
• How many pre-test sessions do you usually hold, and can I take breaks between them?
• Will a neurologist examine me before testing to record a baseline, and what would that involve?
• How will my result be given to me, and can I bring someone?
• Can I decide not to hear the result after the sample has been taken?
• Where will the result be stored, and who in the health system can see it?
• What does a result in the 36 to 39 range mean for me, and how would you counsel me if I received one?
• If my result is positive, what follow-up do you recommend and how often?
• Are there research studies I could join with either result?
• How can I have children without passing on the expansion, and what are the trade-offs of each route?
• Is exclusion testing available if I do not want to know my own status?
• Who can I talk to about insurance and employment questions in my situation?
• What support do you offer for my partner, siblings or children?
• If I decide not to test now, how do I come back later?

Notice that almost none of these questions have a right answer that applies to everyone. That is the point. The care team’s job is to give you the information; the decisions, from whether to test to whom to tell, stay with you and the clinicians who know your history.

When to call your doctor

Genetic counseling is a planned, unhurried process, but certain situations should prompt a same-day call to your doctor, counselor or the neurology team rather than waiting for the next scheduled visit.

• Thoughts of harming yourself or of not wanting to be alive, at any point before or after testing. Mood changes are recognized both as a feature of the condition itself and as a response to the testing process, and help is available quickly. In the United States, the 988 Suicide and Crisis Lifeline can be reached by call or text at any hour; elsewhere, use your local emergency number.
• New involuntary movements, unexplained falls, trouble swallowing or a marked change in speech in someone known to carry the expansion or at risk of it. These warrant a neurological assessment, not self-monitoring.
• Sudden confusion, a severe change in behavior, or a psychiatric crisis in a relative with Huntington’s. Cleveland Clinic and NHS guidance note that these can escalate and need prompt evaluation.
• Choking episodes or unintended weight loss in a person with established disease, since swallowing difficulty carries a real risk of aspiration.
• Any side effect that appears after a medicine is started or adjusted. Do not stop or change a prescribed medicine on your own; contact the prescribing clinician.
• A pregnancy discovered after prenatal or exclusion testing was being considered, since timing windows are narrow.

For anything less urgent, such as questions about insurance, wanting to revisit a decision, or a relative asking to be tested, an ordinary message or booked appointment is the right route. Genetic counseling services expect to hear from families repeatedly over years, and coming back is not an imposition. It is how the process is meant to work.

Frequently asked questions

Is predictive testing for Huntington's available to teenagers?

Predictive testing is generally not offered to people under 18, according to NIH guidance, because a minor cannot fully consent to lifelong information that has no preventive treatment attached. The exception is a child or teenager with possible symptoms of juvenile Huntington’s, where a neurologist may order diagnostic testing as part of a clinical workup. Families can still attend counseling with adolescents to talk through the family history and prepare for a decision at adulthood.

Does a negative result mean my children are safe from Huntington's?

Yes, if your result is in the normal range of 26 or fewer repeats, your children cannot inherit an expansion from you, because you do not carry one. An intermediate result of 27 to 35 is different: you are not expected to develop symptoms, but MedlinePlus Genetics notes the repeat can enlarge when passed on, so a counselor would discuss what that means for your children. Your children could of course still be at risk through their other parent.

Can the test tell me when symptoms will start?

No. The test reports a CAG repeat count, and while larger counts tend to be associated with earlier onset across large groups, the relationship is far too loose to predict an individual’s timeline. Two people with the same number can develop signs decades apart. Counselors describe a positive result as a statement about lifetime probability, not a date, and periodic neurological review is offered to notice changes rather than to count down.

What is exclusion testing in Huntington's prenatal testing?

Exclusion testing checks which grandparent’s copy of chromosome 4 a pregnancy or embryo inherited, without looking for the expansion directly. If the copy came from the unaffected grandparent, the pregnancy is not at risk. If it came from the affected grandparent, the pregnancy carries the same 50 percent risk as the at-risk parent, whose own status stays unknown. It is designed for parents who want to protect their children without learning their own result.

Can I have the test if my parent has never been tested?

Usually yes, but counselors will explore it carefully first. A positive result in you means your at-risk parent almost certainly carries the expansion too, so you would be revealing their status without their consent. Some families talk openly beforehand, some adult children proceed and keep the result private, and some parents choose to test first. There is no rule that forbids testing; there is a strong expectation of honest discussion about the consequences.

Will my result go into my medical record?

In most health systems a genetic result becomes part of your medical record, though some genetics services can hold it in a separate file with restricted access. Ask before the sample is taken. In the United States, MedlinePlus Genetics explains that GINA prevents health insurers and larger employers from using the information, but life, disability and long-term care insurers are not covered by that law, so many people review those policies before testing.

What is the difference between 38 repeats and 42 repeats?

A count of 38 sits in the reduced-penetrance range of 36 to 39, where MedlinePlus Genetics notes that a person may or may not develop symptoms during a normal lifespan. A count of 42 sits in the full-penetrance range of 40 or more, where symptoms are expected. Neither number predicts age of onset for an individual, and both carry a 50 percent chance of being passed to each child, which is why counseling covers both possibilities in advance.

Can I change my mind after the blood is drawn?

Yes. Mainstream protocols allow you to decline to receive the result at any stage, including at the disclosure appointment itself. Some people ask that the result be held on file until they feel ready, and others never collect it. Counselors would rather you pause than hear news you are not prepared for. If you sense hesitation building between the sample and the results appointment, say so; that conversation is exactly what the service is there for.

Do I need to know my status before having children?

No. Families have several routes that do not require the at-risk parent to test, including exclusion prenatal testing, exclusion preimplantation testing with IVF, using donor eggs or sperm, or choosing to conceive without any testing and accepting the 50 percent risk described by MedlinePlus Genetics. Each route has trade-offs in timing, physical demands and certainty, and no fertility option can guarantee an outcome, so counselors encourage raising the question before a pregnancy begins.

How is the Huntington's disease inheritance pattern different from a recessive condition?

Huntington’s is autosomal dominant, meaning one altered copy of the HTT gene is enough to cause disease, and it does not skip generations. Recessive conditions such as cystic fibrosis require altered copies from both parents, so healthy carriers can pass a gene silently for generations. In Huntington’s, a person who does not inherit the expansion cannot transmit it, and an apparent gap in a family tree usually reflects early death from another cause or an intermediate repeat that expanded.

References

• MedlinePlus Genetics: Huntington disease
• NHS: Huntington's disease
• NIH National Institute of Neurological Disorders and Stroke: Huntington's Disease
• MedlinePlus Genetics: What is genetic discrimination?

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.