Why is it not possible to use the FBNI gene to diagnose Marfan syndrome?

Answer 1

It is presently not useful as a diagnostic test because there is evidence that there can be mutations in the fibrillin gene that do not produce Marfan.

Answer 2

The FBNI gene encodes for a protein called fibrillin-1, mutations of which are associated with Marfan syndrome. However, there are other genes also implicated in Marfan syndrome. Therefore, diagnosing Marfan syndrome solely based on FBNI gene mutations may not capture the full spectrum of genetic variations that can cause the condition. A comprehensive genetic testing panel is usually needed for an accurate diagnosis.