these are misnomers actually,when there is no evident cause of hypertension then it is called idiopathic/benign/primary/unspecified hypertension.

http://treathypertension.blogspot.com/

Benign Nephrosclerosis

401.1

Hypertension just means "high blood pressure." Benign hypertension is high blood pressure that "runs a relatively long and symptomless course"--in other words, your blood pressure is high, but it isn't causing any real problems.

More accurately, it isn't causing symptoms. It is causing problems, in that it is damaging your kidneys, heart, and putting you at risk for myocardial infarction (heart attack) and stroke.