Alzheimer disease, early-onset familial: Alzheimer disease that runs in families and strikes at an unusually early age (with its onset under the age of 60). About 7% of early-onset cases of Alzheimer’s are familial and are inherited in an autosomal dominant manner with high penetrance.
Mutations in three different genes — the amyloid precursor protein (APP) gene and the presenilin 1 and 2 (PSEN1 and PSEN2) genes — have been discovered in families with early-onset familial Alzheimer’s disease. Taken together, these mutations only account for about 20-50% of familial Alzheimer’s, indicating that other genes remain to be found in this disorder.
The APP gene encodes the beta-amyloid protein which accumulates abnormally in the brain in Alzheimer’s disease. The protein products of the PSEN1 and PSEN2 genes interact with proteins are involved in signalling processes within and between cells.
Although familial Alzheimer’s disease is responsible for a small minority of cases of Alzheimer’s disease, it is important, not only for the families with it, but also for what we can learn about all of Alzheimer’s disease from it.
- Alzheimer's disease
Alzheimer’s disease: A progressive degenerative disease of the brain that leads to dementia. On a cellular level, Alzheimer’s disease is characterized by the finding of unusual helical protein filaments in nerve cells of the brain. These twisted filaments are called neurofibrillary tangles. In the brain, Alzheimer’s disease involves degeneration of the cortical regions, especially the […]
Amalgam: In dentistry, an alloy of mercury, silver, tin, etc. used in dental restorations.
Amastia: A rare condition wherein the normal growth of the breast or nipple does not occur. Unilateral amastia (just on one side) is often associated with absence of the pectoral muscles. Bilateral amastia (with absence of both breasts) is associated in 40% of cases with multiple congenital anomalies (birth defects) involving other parts of the […]
Amathophobia: An abnormal and persistent fear of dust. Sufferers experience anxiety even though they realize dust poses no threat. From the Greek “amathos” (sand) and “phobos” (fear).
- Amaurosis fugax
Amaurosis fugax: A symptom described as a shade coming down over the eye. A partial or complete loss of sight that is temporary. This temporary interference with vision is usually related to atherosclerosis in the blood vessels that supply the brain. It can also occur with excessive acceleration, as in flight. Amaurosis is the Greek […]