A chromosomal anomaly associated with alzheimer’s dementia is –
**Core Concept**
The question is testing the association between a chromosomal anomaly and Alzheimer's dementia, a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. This involves understanding the genetic basis of Alzheimer's disease, which has been linked to mutations in several genes, including those involved in amyloid precursor protein (APP) processing.
**Why the Correct Answer is Right**
The correct answer is associated with the APOE gene, specifically the APOE ε4 allele, which is a well-established risk factor for late-onset Alzheimer's disease. The APOE gene encodes apolipoprotein E, a protein involved in lipid metabolism and transport. The APOE ε4 allele is thought to contribute to the development of Alzheimer's disease by promoting the formation of amyloid plaques, a hallmark of the disease. This is achieved through the interaction of APOE with the amyloid precursor protein (APP), leading to increased production of amyloid-β, a key component of amyloid plaques.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as there is no established chromosomal anomaly directly linked to Alzheimer's dementia. While Alzheimer's disease has a complex genetic basis, this option does not accurately represent a known risk factor.
**Option B:** This option is incorrect as it refers to a chromosomal deletion syndrome, which is not directly associated with Alzheimer's dementia. While genetic abnormalities can contribute to neurodegenerative disorders, this option is not relevant to the question.
**Option C:** This option is incorrect as it refers to a different type of genetic disorder, not directly linked to Alzheimer's dementia. While genetic mutations can affect various aspects of brain function, this option is not relevant to the question.
**Clinical Pearl / High-Yield Fact**
The APOE ε4 allele is a significant risk factor for late-onset Alzheimer's disease, with a cumulative effect on disease risk as the number of ε4 alleles increases. It is essential to consider APOE genotype when evaluating patients with cognitive decline or dementia.
**Correct Answer: D. APOE gene**