Early-Onset Alzheimer's

Early and late-onset Alzheimer’s have mostly the same symptoms; however, early-onset develops before age 65 and late-onset develops after age 65.
 
Early-onset comes in two forms, either familial or sporadic while Late-onset is sporadic. Carmen suffered from Familial Alzheier’s disease. 
 
Familial Alzheimer's disease (FAD) or early-onset familial Alzheimer's disease (EOFAD) is an uncommon form of Alzheimer's disease that usually strikes earlier in life, defined as before the age of 65 (usually between 30 and 60 years of age) and is inherited in an autosomal dominant fashion, identified by genetics and other characteristics such as the age of onset. Familial AD requires the patient to have at least one first-degree relative with a history of EOAD. FAD usually implies multiple persons affected in one or more generations. Nonfamilial cases of AD are referred to as "sporadic" AD, where genetic risk factors are minor or unclear.
 
While early-onset familial AD is estimated to account for only 1% of total Alzheimer's disease, it has presented a useful model in studying various aspects of the disorder. Currently, the early-onset familial AD gene mutations guide the vast majority of animal model-based therapeutic discovery and development for AD.



Clinical features

Alzheimer's disease (AD) is the most common cause of dementia and usually occurs in old age. It is invariably fatal, generally within 10 years of the first signs. Early signs of AD include unusual memory loss, particularly in remembering recent events and the names of people and things, logopenic primary progressive aphasia. As the disease progresses, the patient exhibits more serious problems, becoming subject to mood swings and unable to perform complex activities such as driving. Other common findings include confusion, poor judgement, language disturbance, agitation, withdrawal, hallucinations, seizures, Parkinsonian features, increased muscle tone, myoclonus, incontinence, and mutism. In the latter stages, they forget how to do simple things such as brushing their hair and then require full-time care.
 
Histologically, familial AD is practically indistinguishable from other forms of the disease. Deposits of amyloid can be seen in sections of brain tissue. This amyloid protein forms plaques and neurofibrillary tangles that progress through the brain. Very rarely, the plaque may be unique, or uncharacteristic of AD; this can happen when a mutation occurs in one of the genes that creates a functional, but malformed, protein instead of the ineffective gene products that usually result from mutations.
 
The underlying neurobiology of this disease is just recently starting to be understood. Researchers have been working on mapping the inflammation pathways associated with the development, progression, and degenerative properties of AD. The major molecules involved in these pathways include glial cells (specifically astrocytes and microglia), beta-amyloid, and proinflammatory compounds. As neurons are injured and die throughout the brain, connections between networks of neurons may break down, and many brain regions begin to shrink. By the final stages of Alzheimer's, this process - called brain atrophy - is widespread, causing significant loss of brain volume. This loss of brain volume affects one's ability to live and function properly, ultimately being fatal.
 
Beta-amyloid is a small piece of a larger protein called amyloid precursor protein (APP). Once APP is activated, it is cut into smaller sections of other proteins. One of the fragments produced in this cutting process is β-amyloid. β-amyloid is “stickier” than any other fragment produced from cut-up APP, so it starts an accumulation process in the brain, which is due to various genetic and biochemical abnormalities. Eventually, the fragments form oligomers, then fibrils, beta-sheets, and finally plaques. The presence of β-amyloid plaques in the brain causes the body to recruit and activate microglial cells and astrocytes.
 


Genetics

Familial Alzheimer disease is caused by a mutation in one of at least three genes, which code for presenilin 1, presenilin 2, and APP. Other gene mutations are in study.

 

Sources:
Helix.com
Wikipedia