Alzheimer’s disease is found to occur in three forms.

1) Early-onset Alzheimer’s disease
2) Late-Onset Alzheimer’s disease
3) Familial Alzheimer’s disease

Early-onset Alzheimer’s disease: A rare form of the disease, it has hit less than one tenth of all Alzheimer’s patients. People who get Early-onset Alzheimer’s disease are diagnosed always before the age of 65. When this is diagnosed at a younger age, the patient tends to have the brain abnormalities that lead to it. The cause is largely genetic with chromosome 14 being the root of the problem. Myoclonus is one of the symptoms of this form of Alzheimer’s disease.
It is basically the result of the mutation of three genes – presenilin 1, presenilin 2 and amyloid precursor protein. Research has shown that they are of no danger at all when separate but are the source of the disease unlike when together. People who suffer from this form of the disease are the kind who find it difficult it to do the simplest of things, go through many number of personality changes, who can’t really remember much – short and long term and who get very easily confused.

Be on the lookout for muscle twitching and also for spasms as they are early sign of Early-onset Alzheimer’s disease.
Late-onset Alzheimer’s disease: The most found form of Alzheimer’s disease, it accounts for accounting for about 90% of Alzheimer’s. These cases are distinctly occurring post 65 years of age. It is there in almost all people who crossed the age of 85. This kind of Alzheimer’s is not necessarily and may or may not be hereditary. It is also called sporadic Alzheimer’s disease.

Sadly, research has not been fruitful to determine the one single reason for the occurrence of Late-onset Alzheimer’s disease. The closest that researchers have to come to a solution is that the risk factor is gene dominated. The Apolipoprotein E (ApoE) works for and against Late-onset Alzheimer’s. The gene’s e4 type plays a larger role in causing for it while the e2 type plays one working against it. At the end of the day, the presence of this gene indicates danger of getting the disease. The effect of the gene can be lessened by use and presence of toxins, changing of the environment and adopting the right lifestyle in order to do so.

Familial Alzheimer’s disease(FAD): It is an inherited form of Alzheimer’s disease that is completely genetical. In families that have been hit by FAD, two members have been affected by default. The exact problem with the genes is that a genetic fault is passed down the family in certain particular chromosomes. Studies have showed that to be 21, 14 or 1.
It is very uncommon making up less than one per cent of the cases of Alzheimer’s disease. It can kick in as early as the 30’s and the 40’s in this case.