Alzheimer disease, type 4

Alzheimer disease, type 4 is an early-onset, familial form of Alzheimer disease. It is similar to other forms of early onset Alzheimer disease, but each type is caused by mutations in a different gene. This degenerative disease of the brain causes gradual loss of memory, judgment, and ability to function socially.

Alzheimer disease, type 4 is a subtype of Alzheimer disease.

As in the other types of Alzheimer disease, the most common sign of type 4 Alzheimer disease is memory loss. The disorder usually develops between the ages of 40 and 75 years. The course of the disease averages 11 years, and death most often results from pneumonia, malnutrition, or general body wasting. For additional information about the symptoms of this disorder, please refer to the Alzheimer disease summary.

Early-onset familial Alzheimer disease accounts for less than 2 percent of all cases of Alzheimer disease. Alzheimer disease, type 4 has been identified in only a few families worldwide. It accounts for less than 5 percent of all cases of early-onset familial Alzheimer disease.

Mutations in the PSEN2 gene cause Alzheimer disease, type 4.

The PSEN2 gene produces a protein called presenilin 2. Mutations in the PSEN2 gene alter presenilin 2, which leads to increased production of a protein fragment called amyloid beta peptide (a substance found in the brain and other tissues). This peptide can build up in the brain to form clumps called amyloid plaques, which are characteristic of Alzheimer disease.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to cause the disorder.

You may find the following resources about Alzheimer disease, type 4, helpful.

• NIH Publications - National Institutes of Health (2 links)
• MedlinePlus - Health Information (2 links)
• Genes and Disease - Genetic disorder summaries
• Patient support - For patients and families (4 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• ClinicalTrials.gov - Linking patients to medical research
• PubMed - Recent literature
• OMIM - Genetic disorder catalog

See How are genetic conditions and genes named? in the Handbook.

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

amyloid ; amyloid plaque ; autosomal ; autosomal dominant ; degenerative ; dementia ; familial ; gene ; mutation ; peptide ; protein ; sign ; symptom ; wasting

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.