ApoE susceptibility testing is more relevant for late-onset AD and for AD that is inherited in a non-Mendelian fashion than for eFAD, and is therefore not discussed in detail here. Genetic testing is also available for other forms of hereditary dementia, for example Creutzfeldt-Jakob disease and frontotemporal dementia, as well as for some forms of inherited Parkinson disease. The specific details differ for each disease, depending on its underlying genetics, but the general issues are similar.
Clinical practice on this is not uniform, as some physicians believe that genetic testing has value, while others feel that it adds little. Typically, doctors only recommend this if there is a previous known case of AD in the family. That affected person donates blood, which is then tested for a mutation in the genes for presenilin 1, presenilin 2, or APP. In the U.
STD Panel: Order Full Test Panel for 10 Common STDs
Testing for the last two genes must be pursued through an academic laboratory. If these tests come back negative, the question of a possible genetic cause of AD in the family stays unanswered. If they come back positive, the doctor can identify the mutation that causes AD in the family. Once a mutation is found, doctors can test if the same mutation occurs in the DNA of additional family members.
In those instances where a mutation is found in a fully diagnosed AD case, DNA testing can then complete the diagnosis in other members of the family. Some clinicians think this can be particularly helpful when a relative has early symptoms and s he, or the spouse and siblings, suspect AD but would not otherwise be able to know definitively for a few more years until symptoms become overt. Those are angst-ridden years for the family, and testing can lay an agonizing uncertainty to rest.
It can also help people with early AD psychologically, as it confirms that their difficulties are not their fault, and that they were right to cut back work if they had to. For some people, the test result helps them plan their future and focus on creating good times with their families.
Occasionally, medical geneticists use diagnostic testing in a slightly broader way. They sometimes search the DNA of a person in whom they suspect AD for eFAD mutations even when there is not a clear autosomal-dominant inheritance pattern in the family, or in cases where a parent who had early onset dementia has died and no blood or tissue samples from the parent are available for testing.
Popular in: Diabetes
This can then help diagnose further cases of AD in relatives. This kind of search is best done by specialized research groups, who are adept at distinguishing an inconsequential gene change from a true AD mutation e. Diagnostic DNA testing is done most commonly on the presenilin 1 gene. CLIA-certified labs can formally confirm mutation findings that cropped up first in the context of a research study. Mutations in these two genes are rarer than presenilin 1 mutations. No commercial test is available for them, and testing occurs at various academic centers.
Clinicians disagree about whether that is good or bad. At the same time, researchers are mindful that the genetics of AD is more complicated to interpret than that of some other heritable diseases, such as Huntington's. Some AD clinical geneticists worry that if tests results were available too easily, people might end up receiving misleading results. ApoE testing sometimes becomes part of the diagnostic workup of a person with eFAD. ApoE comes in three types 2, 3, and 4.
In the general population, people with ApoE4 face a greater risk of developing AD at a younger age. Some clinicians feel that in a person with an autosomal-dominant eFAD mutation, ApoE genotyping can give some added insight into when AD is likely to begin or how aggressive its course is likely to be. However, in those cases the impact of the primary eFAD mutation far outweighs that of ApoE4, and indeed other clinicians argue that ApoE testing adds little information for these particular families.
Some research studies are exploring differences in how ApoE variants affect a person's response to a given therapeutic drug. Once this research solidifies, ApoE testing may add real value to the diagnosis. Until then, it is up to the discretion of the medical team. In general, medical centers offer genetic testing as a clinical service. Patients would be required to pay for the diagnostic test out of pocket or through their health insurance. A few centers have research studies that can cover the cost of genetic testing for volunteers who agree to participate in a study.
In this setting, the researchers need to know which participants carry an eFAD mutation, but not every participant will want to know.
- Important Resources.
- Schelmpflicht: Wortspiel ist reinmeingebiet (German Edition);
- From a Land Far, Far Away!
- Chloride Sweat Test.
- Navigation menu.
Participants can choose whether or not to be told their test results. Part of the reason why people choose to get tested in a research setting is that this information need not become part of their medical record. Each route to genetic testing—clinical service vs. It has a clear-cut benefit—after all, nailing an uncertain, difficult diagnosis in someone who is already ill offers clarity for all. But nothing in genetic testing is absolute, and there are situations where diagnostic testing may do more harm than good.
This is a danger in "sporadic" cases. The news of a wholly unexpected AD gene in mom or dad, or a sibling with children, would be a bombshell for the family. It's sure to upset children, siblings, and possibly even relatives further removed. Why test DNA in sporadic cases? Familial Alzheimer disease is genetic and sporadic disease is not—right? This widely held assumption is in fact an arbitrary division and is not always true. Granted, clinicians most readily suspect a faulty gene when early onset AD has shown a pattern of reappearing in the family.
Preventive healthcare - Wikipedia
But on occasion they are also ordering a genetic test in cases where their patient is the only known sufferer. As AD genetics become better known, some physicians send blood for testing simply because a person's symptoms begin unusually early. With some regularity, back comes news of a presenilin mutation. This can be useful in making the correct diagnosis, but it's dangerous, too. If the physician isn't careful, s he might end up springing a terrible surprise on unsuspecting young adult children, namely a 50 percent risk of carrying a gene for AD themselves.
Where the clinical team suspects that "sporadic" AD is not actually sporadic, it's important that they move cautiously and give the family ample opportunity to come to terms with this new prospect. Depending on the family's circumstances, the delicate balance of a physician's duty to warn versus a family's right not to know may come down on the side of doing less rather than more. Consider some examples. Genetic counselor Jill Goldman, then at the University of California, San Francisco, and her colleagues there recently explored this issue with a series of case reports.
One tells the story of a year-old Hispanic immigrant who had had early onset AD for 12 years when her husband and daughter brought her in. The family had no health insurance and paid for the visit out of pocket. A genetic counseling session soon made clear that they were neither prepared to learn of the potential risk to their family, nor in a position to benefit from a genetic diagnosis. They worried about the cost of the test and about having to scare their relatives.
For them, it seemed as if any further disclosure of genetic risk might cause mostly disruption and anxiety. The father and daughter decided against genetic testing. The question that lingered with Goldman was, How can the physician and counselor know beforehand if the caregivers want to be made aware of a possible genetic burden and its implications for the rest of the family?
In other words, did this family want to know even as much as they heard in their initial counseling session? Moreover, cultural attitudes to medical knowledge and family structures in different ethnic backgrounds are an important part of this equation. In most situations, discussions about genetic testing in families with sporadic cases of dementia should be delayed until the utility and benefits can be established and a long-term relationship with the patient and family can be developed," the authors write Goldman and Hou, A further facet of this issue emerges from the story of a patient with Creutzfelt-Jakob disease CJD , a degenerative prion disorder in the group of diseases that includes "mad cow" disease.
It poses similar genetic dilemmas. At 53, the man appeared to have CJD. His year-old daughter signed an informed consent for his participation in a research study that included genetic testing, and a known mutation in his prion gene turned up. The daughter was stunned to learn, rather abruptly, that her own odds of getting CJD were To her knowledge, her family had never experienced neurologic disease before. The medical team offered predictive testing to the daughter in the context of a full counseling protocol, and after several weeks of consideration, she opted in.
The point here is that this woman did not have a chance to make an informed decision about whether she wanted to know her father's status or not. It just came out in the course of reviewing his records. The third story tells of a year-old woman with CJD that seemed sporadic. A local physician sent blood off for genetic testing without prior genetic counseling with the patient or her husband.
Before the family found out this test result, the patient happened to be referred to UCSF for a research study.
You and Your Family
In its course, the patient, his wife, and their adult daughter and son-in-law entered genetic counseling, which opened their eyes to the full import of knowing the patient's genetic status. The daughter was expecting a baby, and the family decided they did not want to know the patient's genetic result at that time.
The family then had to instruct their local physician to withhold the genetic result.
- The Anxiety Book: Developing Strength in the Face of Fear.
- Can diabetes be passed down in the genes?!
- This Crazy Love: A Collection Of Poetry?
- Infectious disease testing?
- Why it's done.
Sometimes people get tested twice: the local physician had ordered the test clinically, whereas the researchers would have performed it in an academic setting without disclosing its result to the family. The fourth case showcased how genetic testing can fray the family fabric.
A year-old patient came in with his wife, adult son, and daughter. He received a diagnosis of probable AD. The family knew of no relatives with AD but chose to have the father tested because his symptoms started at When the family learned he did indeed have a presenilin mutation, disagreements arose.
This is a problem with diagnostic testing: it puts on the table the option of predictive testing for relatives, and family dynamics around that can be fraught. In this case, the parents were upset at the risk for their children and did not want them tested. In individual counseling sessions, the daughter, too, said she did not want to know her status, nor her brother's.
Yet the son insisted he wanted to find out. He entered the full genetic counseling program but eventually withdrew under pressure from his family Goldman et al. Other investigators, too, have reported that many families communicate poorly about their genetic burden and tend to avoid the issue rather than face it openly.
The lesson from these four case vignettes is that families who have for years, or generations even, watched AD claim loved ones and cared for them, tend to be aware that something is up genetically. They are somewhat prepared to handle concrete information about it and tend to welcome the genetic validation after years of torment. By contrast, relatives of sporadic cases tend to be unprepared for the idea of an incurable brain disease in their family.
For them the realization can bring more shock than relief.
Related Genetically Transmitted Diseases - 5 Minute prep for the Medical Exams !!
Copyright 2019 - All Right Reserved