Rare familial form of Alzheimer's disease:Disease-causing changes occur mainly in three genes: the App gene, the Presenilin1 gene (most common), the Presenilin2 gene (the rarest). All of the mutations found in the three genes increase the production and deposition of beta-amyloid in the affected person's brain.
Common sporadic form of Alzheimer's disease: The gene variant APOE 4 is one of the biggest risk factors for Alzheimer's if it occurs twice, ie one copy each was inherited from the father and one from the mother. More than 40 percent of Alzheimer's sufferers have two copies of APOE 4.
Another gene, a variant of TREM 2, poses as high a risk of Alzheimer's disease as APOE 4. TREM 2 plays an important role in the microglial cells, the phagocytes of the brain.
Protective gene modifications are also known. This includes the APOE3 / Christchurch mutant of the Colombian woman. It was known that also the variant APOE2 protects in duplicate. In the Icelandic population, as well as in Finland, Norway and Sweden, researchers found another rare gene change. It concerns the APP gene. However, thanks to this change, the carriers produce less beta amyloid. (AFO)