ALZHEIMER’S DISEASE

GENETICS OF THE DISEASE

• Alzheimer disease (AD) is the most common causes of neurodegenerative disorder in the elderly individuals. Clinically, patients initially present with short-term memory loss, subsequently followed by executive dysfunction, confusion, agitation, and behavioral disturbances. Three causative genes have been associated with autosomal dominant familial AD (APP, PSEN1, and PSEN2) and 1 genetic risk factor (APOEε4 allele). Identification of these genes has led to a number of animal models that have been useful to study the pathogenesis underlying AD. In this article, we provide an overview of the clinical and genetic features of AD.

• Overall, more than 90% of patients with AD appear to be sporadic and to have a later age at onset of 60 to 65 years of age (LOAD).38 Although twin studies support the existence of a genetic component in LOAD, no causative gene has been yet identified. Indeed, the only gene that has been consistently found to be associated with sporadic LOAD, across multiple genetic studies, is the apolipoprotein E (APOE) gene39–43 (Table 1). However, many carriers of the APOE risk allele (ε4) live into their 90s, which suggests the existence of other LOAD genetic and/or environmental risk factors that have yet to be identified. To this end, several unreplicated genetic variants have been reported, and these findings suggest that there may be 5 to 7 major LOAD susceptibility genes

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CAUSE OF DISEASE

• The exact causes of Alzheimer’s disease aren’t fully understood. But at a basic level, brain proteins fail to function normally, which disrupts the work of brain cells (neurons) and triggers a series of toxic events. Neurons are damaged, lose connections to each other and eventually die.��Scientists believe that for most people, Alzheimer’s disease is caused by a combination of genetic, lifestyle and environmental factors that affect the brain over time.��Less than 1% of the time, Alzheimer’s is caused by specific genetic changes that virtually guarantee a person will develop the disease. These rare occurrences usually result in disease onset in middle age.��The damage most often starts in the region of the brain that controls memory, but the process begins years before the first symptoms. The loss of neurons spreads in a somewhat predictable pattern to other regions of the brains. By the late stage of the disease, the brain has shrunk significantly.

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SYMPTOMS

• mental decline, difficulty thinking and understanding, confusion in the evening hours, delusion, disorientation, forgetfulness, making things up, mental confusion, difficulty concentrating, inability to create new memories, inability to do simple maths, or inability to recognise common things�Behavioural: aggression, agitation, difficulty with self care, irritability, meaningless repetition of own words, personality changes, restlessness, lack of restraint, or wandering and getting lost�Mood: anger, apathy, general discontent, loneliness, or mood swings�Psychological: depression, hallucination, or paranoia�Also common: inability to combine muscle movements, jumbled speech, or loss of appetite�

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DIAGNOSIS

• An important part of diagnosing Alzheimer’s disease includes being able to explain your symptoms, as well as perspective from a close family member or friend about symptoms and their impact on daily life. Additionally, a diagnosis of Alzheimer’s disease is based on tests your doctor administers to assess memory and thinking skills.
• Laboratory and imaging tests can rule out other potential causes or help the doctor better identify the disease causing dementia symptoms.�But Alzheimer’s disease is only diagnosed with complete certainty after death, when microscopic examination of the brain reveals the characteristic plaques and tangles.

TREATMENT

• Drugs�Current Alzheimer’s medications can help for a time with memory symptoms and other cognitive changes. Two types of drugs are currently used to treat cognitive symptoms:�Cholinesterase inhibitors. These drugs work by boosting levels of cell-to-cell communication by preserving a chemical messenger that is depleted in the brain by Alzheimer’s disease. These are usually the first medications tried, and most people see modest improvements in symptoms.�Cholinesterase inhibitors may also improve neuropsychiatric symptoms, such as agitation or depression. Commonly prescribed cholinesterase inhibitors include donepezil (Aricept), galantamine (Razadyne) and rivastigmine (Exelon).�The main side effects of these drugs include diarrhea, nausea, loss of appetite and sleep disturbances. In people with certain heart disorders, serious side effects may include cardiac arrhythmia.�Memantine (Namenda). This drug works in another brain cell communication network and slows the progression of symptoms with moderate to severe Alzheimer’s disease. It’s sometimes used in combination with a cholinesterase inhibitor. Relatively rare side effects include dizziness and confusion.

• You can take these steps to support a person’s sense of well-being and continued ability to function:�Always keep keys, wallets, mobile phones and other valuables in the same place at home, so they don’t become lost.�Keep medications in a secure location. Use a daily checklist to keep track of dosages.�Arrange for finances to be on automatic payment and automatic deposit.�Have the person with Alzheimer’s carry a mobile phone with location capability so that a caregiver can track its location. Program important phone numbers into the phone.�Install alarm sensors on doors and windows.�Make sure regular appointments are on the same day at the same time as much as possible.�Use a calendar or whiteboard in the home to track daily schedules. Build the habit of checking off completed items.�Remove excess furniture, clutter and throw rugs.�Install sturdy handrails on stairways and in bathrooms.�Ensure that shoes and slippers are comfortable and provide good traction.�Reduce the number of mirrors. People with Alzheimer’s may find images in mirrors confusing or frightening.�Make sure that the person with Alzheimer’s carries identification or wears a medical alert bracelet.�Keep photographs and other meaningful objects around the house.

@mayo clinic

• Submitted by,

YADHUKRISHNAN. T. P

3^rd BSC ZOOLOGY

Roll no. 26

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