What is true about multifactorial diseases?

Multifactorial diseases are characterized by the interplay of multiple genetic and environmental factors in their development. One of the defining features of these diseases is their tendency to cluster in families, indicating that both genetic predisposition and shared environmental influences contribute to the risk of developing such conditions. This familial clustering can be observed in various multifactorial disorders like heart disease, diabetes, and certain types of cancer, where family history plays a significant role in assessing individual risk.

The first statement about these diseases being caused solely by single gene defects is incorrect, as multifactorial diseases arise from the interaction of several genes, rather than a single gene mutation. The assertion regarding the absence of a genetic component is also misleading; multifactorial diseases indeed have a genetic basis, although it is more complex than in single-gene disorders. Finally, while some multifactorial conditions can affect older adults, they can also manifest earlier in life, and the age of onset can vary greatly depending on the specific disease and individual factors.