Alzheimer's disease usually starts with symptoms that are subtle and therefore poorly recognized, such as memory failure.
Alzheimer's disease (AD) is characterized by adult onset progressive dementia that is associated with beta-amyloid plague formation, cerebral cortical atrophy, and intraneuronal neurofibrillary tangles. AD commonly starts with memory failures that are subtle and then become more severe, eventually becoming incapacitating. Additional finding that are common include poor judgment, confusion, agitation, language disturbance, hallucinations, withdrawal, Parkinsonian features, seizure activity, myoclonus, increased muscle tone, mutism, and incontinence. Familial AD characterizes families that have more than one person in the family with AD and typically implies multiple persons who are affected across more than one generation in the family. Early-onset familial AD refers to families where onset of the disease consistently occurs prior to the age of sixty to sixty-five years and many times before the age of fifty-five.
Symptoms of EOAD
Alzheimer's disease usually starts with symptoms that are subtle and therefore poorly recognized, such as memory failure. Slowly, and often over a period of years, the person's memory loss becomes increasingly severe, eventually becoming incapacitating. Other symptoms that are common to Alzheimer's disease include:
Increased Muscle Tone
People affected by Alzheimer's disease who die commonly perish as a result of malnutrition, general inanition, and pneumonia.
Causes of EOAD
Medical science has identified three genes that are associated with early-onset familial Alzheimer's disease. These genes include:
PSEN1: Mutations of this gene are associated with Alzheimer's disease type 3, which accounts for thirty to seventy-percent of early-onset familial Alzheimer's disease.
PSEN2: Mutations in this gene are associated with Alzheimer's disease type 4. PSEN2 has been identified by the medical community in a few families living in the United States, in three Italian kindreds, in two Italian kindreds, and in two Spanish families. Mutations in PSEN2 account for less than five-percent of all early-onset familial Alzheimer's disease.
APP: Mutations in this gene are associated with Alzheimer's disease type 1, which accounts for approximately ten to fifteen-percent of early-onset familial Alzheimer's disease.
Kindreds with autosomal dominant early-onset familial Alzheimer's disease who do not have identifiable mutations in PSEN1, PSEN2, or APP genes have also been described. It is likely that mutations in other genes are a cause of EOAD.
A diagnosis of early-onset Alzheimer's disease can be obtained in families that have multiple members who are affected by the disease with a mean age onset of before age sixty-five who have a documented, disease-causing mutation in one of the genes that are known to be associated with the disease. There are three clinically indistinguishable subtypes of early-onset Alzheimer's disease based on the underlying mechanism. These subtypes include:
Alzheimer disease type 1 (AD1), caused by mutations in APP
Alzheimer disease type 3 (AD3), caused by mutations in PSEN1
Alzheimer disease type 4 (AD4), caused by mutations in PSEN2
There are molecular genetic tests for PSEN1, PSEN2, and APP available for families through clinical laboratories.
Alzheimer's disease can be diagnosed in people who present with slowly progressing dementia with an absence of other causes of the dementia, and cerebral cortical atrophy through neuroimaging studies. A post-mortem diagnosis can be achieved through an examination that reveals intraneuronal neurofibrillary tangles and beta-amyloid neuritic plaques.
Treatment of EOAD
Treatment of Alzheimer's disease is largely supportive. Treatment for aggression, depression, seizure activity, sleep disturbances as well as any hallucinations the person may experience are all managed on an individual basis. People who are affected by Alzheimer's disease eventually require the services of either assisted living, a nursing home, or other forms of long-term care services. They require agents that increase cholinergic activity such as donepezil, galatamine, or rivastigmine that tend to provide some, yet variable benefit. There is a medication called, 'memantine,' that is an NMDA receptor antagonist, approved for use with Alzheimer's disease as well. People affected by Alzheimer's disease may benefit from occupational and physical therapies to assist with management of activities of daily living. They should avoid over-sedation and sudden changes to their environment.
Early-onset Alzheimer's disease is inherited in an autosomal dominant manner, meaning that the majority of people with EOAD have a parent who has been affected by the disease. On occasion, neither of a person's parents has been identified as having the disease, although a second-degree relative, such as an uncle, an aunt, or perhaps a grandparent, has or experienced early-onset Alzheimer's disease. Children of people with EOAD have a fifty-percent chance of inheriting the gene mutation for the disease and developing EOAD. Prenatal testing for mothers who are at increased risk of having a child with EOAD with a PSEN1 mutation is available. Prenatal testing for mothers who are at increased risk of having a child with a PSEN2 or APP mutation might be available through laboratories that offer custom prenatal testing. Prenatal testing for adult-onset disorders; however, is unusual.
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