To screen for a rare mutation in the PSEN1 gene known to be associated with Early Onset Familial Alzheimer’s Disease (EOFAD).
Some research has also identified associations in PSEN1 mutations to hidradenitis suppurativa, a chronic inflammatory skin disease. In individuals with this condition, it is used to establish the cause of inheritance.
If you are an adult who has symptoms of dementia and a strong family history of early onset Alzheimer’s Disease (AD that begins before age 60-65) or if you are an adult with no symptoms but with an identified PSEN1 genetic mutation (and EOFAD) in your family.
Eligibility for testing in those with hidradenitis suppurativa include a clinical diagnosis of hidradenitis suppurativa and evidence of autosomal dominant inheritance in two or more relatives over two generations or more.
A blood sample taken from a vein in your arm.
None.
On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.
If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.
Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.
Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.
For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.
For more information on reference ranges, please read Reference Ranges and What They Mean.
This test looks for mutations in the PSEN1 gene, which have been associated with Early Onset Familial Alzheimer’s Disease (EOFAD). Although most AD starts after the age of 65 (late onset), about 5-10% of cases of the disease begin in people under 65 years of age. The majority of these patients present in their 40s or 50s however it is possible for those in their 20s and 30s to experience disease onset. Much of this early onset AD is inherited - it runs in families and is caused by a genetic mutation. There have been three genes identified so far that are associated with EOFAD; all are very rare - accounting for less than one in 1000 cases of Alzheimer's disease. Of these, PSEN1 is the most common and is thought to cause about half the cases of EOFAD. Since PSEN1 is a dominant gene, it only takes one mutated copy, inherited from either your mother or father, to cause EOFAD. Why PSEN1 is associated with EOFAD is not yet known. It is thought that the normal role of the PSEN1 gene is to make the protein presenilin 1, a protein used in the development of the brain and spinal cord. It also works with other enzymes to cut certain proteins into smaller pieces (amyloid beta peptide). A mutation of PSEN1 produces an abnormal presenilin 1 protein that no longer functions properly, resulting in a breakdown of this process. This breakdown lends itself to increased production of the longer, stickier configuration of the amyloid beta protein, which is toxic to the nervous system and eventually forms the characteristic amyloid plaques of AD. Research has identified approximately 300 mutations in PSEN1 so far, however it is considered a rare mutation.
The PSEN1 genetic mutation analysis is new and not widely accepted yet. In its present form, it is only capable of identifying about 30-60% of patients who have EOFAD. The analysis is made easier if a patient already has an identified PSEN1 mutation in their families.
Approximately 40% of hidradenitis suppurativa cases in Western countries are thought to be familial. However, the proportion of these that are caused by mutations in PSEN1 is not known. PSEN1 forms part of the gamma-secretase complex which is integral to transmembrane proteins. It has been hypothesised that mutations lead to disruptions in cell signalling therefore altering skin homeostasis and contributing to the phenotypic traits of hidradenitis suppurative. The utility of PSEN1 mutation analysis in this condition has not been fully elucidated.
This test is not readily available in the UK however, if required under special circumstances a blood sample is obtained by inserting a needle into a vein in your arm.
No test preparation is needed.
PSEN1 genetic mutation analysis is not readily available in the UK. It has the potential to be used to screen asymptomatic (without symptoms) or symptomatic adults (with symptoms) who have a strong family history of early onset familial Alzheimer’s Disease (EOFAD), especially when a PSEN1 mutation has been identified in other family members. It may be used to aid in the diagnosis of early onset Alzheimer’s Disease (versus some other form of early onset dementia) but usually only in those with a family history of EOFAD. PSEN1 is also occasionally used with genetic counselling to assess the risk of having and passing on a PSEN1 mutation to your unborn child. PSEN1 genetic mutation analysis may also be used to identify a familial cause of hidradenitis suppurativa, however this is not routinely available in the UK.
The test can be used in asymptomatic or symptomatic adults with a strong family history of early onset Alzheimer’s Disease, especially when there are multiple family members in multiple generations (preferably three generations) who have had EOFAD. It is NOT useful as a screen for the general population or for those who have late onset AD.
In hidradenitis suppurativa, testing may only occur if a clinical diagnosis of hidradenitis suppurativa has been made and there is evidence of autosomal dominant inheritance in two or more relatives over two generations or more.
If you have one of the PSEN1 mutations, it is highly likely that you will eventually develop EOFAD, usually at a similar age to other affected family members. The 'penetrance' of the gene (symptoms, severity, and rate of progression), however, can vary from individual to individual. Since it is a dominant gene, if you have a PSEN1 mutation, each of your children will have a 50% chance of having the PSEN1 mutation passed on to them.
It should be remembered that the PSEN1 genetic mutation analysis, in its current form, is only capable of picking up 30-60% of EOFAD. If your test is negative, there is still a chance that you have an unidentified mutation.
In hidradenitis suppurativa, the presence of a PSEN1 genetic mutation identifies a possible cause of familial inheritance however it should be used after clinical diagnosis of the disease.
PSEN1 genetic mutation is almost exclusively family-related and is not associated with late onset AD. A few cases of PSEN1 genetic mutation will show up without a strong family history because of 'alternate' paternity, new mutations, or because a parent died before symptoms developed so this element of the family history was unknown.
The PSEN1 test is a new, relatively expensive test that has limited use and is still very rarely used. It is performed in only a few laboratories in the world, so if your doctor recommends the test, your blood sample will need to be sent to a reference lab and results may take a while to return.
No, the symptoms for EOFAD, sporadic early onset AD, and late onset AD are the same except for the age of onset. You cannot tell whether someone has a genetic mutation just by looking at them. If there is a strong family history of early onset AD, and especially if another family member has been diagnosed with a genetic mutation, your doctor may suspect a genetic problem, but a blood test is the only way to confirm this suspicion.
The other genes that have mutations associated with EOFAD are PSEN2 and APP (amyloid precursor protein). PSEN2 testing is available, but APP is still being researched. It should be noted that PSEN2 and APP mutations are very rare. They have only been identified in a very small number of specific family lines.
On This Site
Tests: ApoE, Tau Protein
Conditions: Alzheimer’s disease
Elsewhere On The Web
Alzheimers Society
Dementia Web
Alzheimer’s Research UK
