Alzheimer disease (AD) is a degenerative disease of the brain that causes dementia, which is a gradual loss of memory, judgment, and ability to function. This disorder usually appears in people older than 65 years old, but less common forms of the disease (<10% of cases) appear earlier in adulthood, between a person’s thirties and mid-sixties. It is caused by pathological accumulation of β-amyloid plaques and intraneuronal neurofibrillary tangles (containing tau protein) in the brain, causing the gradual death of brain nerve cells.
Alzheimer disease can be distinguished in late onset (>65 years) and early onset (<65 years) disease.
Late onset Alzheimer disease (type 2)
Late onset AD is the most common form of the disease. It is characterised as complex disorder, where multiple susseptibility genes together with lifestyle and environmental factors define a person’t risk of developing Alzeimer disease.
Apolipoprotein gene E (APOE) has been studied extensively as a risk factor for the disease. APOE gene has 3 different alleles E2, E3 and E4. Carrying one E4 allele is considered to confer a twofold increase of a person’s risk to develop the disease, while carying two E4 alleles leads to a 12-fold increase in the risk for AD.
Method: Typing of APOE alleles E2, E3 and E4 using ARMS-PCR
Time to result: 2 weeks
Early onset Alzheimer disease
Early onset Alzheimer disease is diagnosed in individuals younger than 60 years and accounts for approximately 5-10% of AD cases. Some of the patients carry mutations in the three genes mentioned below, that are inherited in an autosomal dominant manner. Mutations in these genes influence the production of β-amyloid and contribute to the distruction of nerve cells.
Alzheimer disease type 1 (AD1)
Is caused by mutations in ΑΡΡ gene (Amyloid Precursor Protein) and accounts for 10% -15% of early onset AD cases.
Alzheimer disease type 3 (AD3)
Is caused by mutations in PSEN1 gene (Presenilin 1) and accounts for 30% -70% of early onset AD cases.
Alzheimer disease type 4 (AD4)
Is caused by mutations in PSEN2 gene (Presenilin 2) and accounts for approximately 5% of early onset AD cases. Mutations in the same gene have also been reported in individuals with late onset AD.
Method: The analysis of APP, PSEN1 and PSEN2 genes is carried out using Next Generation Sequencing technique.
Time to result: 4 weeks