What is the recurrence risk for late-onset Alzheimer's disease with one affected sibling?

In assessing the recurrence risk for late-onset Alzheimer's disease when there is one affected sibling, research indicates that the risk is relatively low compared to early-onset forms of the disease. Late-onset Alzheimer's typically has a genetic component associated with the apolipoprotein E (APOE) gene, particularly the APOE ε4 allele, which can increase susceptibility but does not follow a simple Mendelian inheritance pattern.

For a person with one affected sibling, the recurrence risk is about 2%. This figure is derived from studies showing that first-degree relatives of individuals with late-onset Alzheimer's disease have a higher risk than the general population. The complexities of polygenic contributions and environmental factors also play a role in familial aggregation, but the established recurrence risk provides a general guideline for understanding familial patterns.

This is why the answer reflects a nuanced understanding of late-onset Alzheimer's inheritance and risk assessment, emphasizing the importance of genetic counseling in evaluating family history and potential risks for relatives.