An object of the present invention is to elucidate the onset mechanism of MSA through specification of a causative gene of it and further, to find a treatment method of it. The present invention provides a method for testing a multiple system atrophy risk of a test subject including a step of detecting a variant that deteriorates the biosynthesis of coenzyme Q10 in a sample collected from the test subject. Examples of the variant that deteriorates the biosynthesis of coenzyme Q10 include variants that suppress the expression or function of coenzyme Q2.
