Final answer:
The client's condition with elevated blood pressure and no symptoms or known cause is described as primary hypertension. This is the most common form of high blood pressure and arises due to genetic and lifestyle factors.
Step-by-step explanation:
A client who has been diagnosed with hypertension, featuring an elevated blood pressure with no symptoms and uncertain cause, is most accurately described as having primary hypertension. Primary hypertension, which accounts for at least 90% of hypertension cases, arises from a combination of genetic and lifestyle factors, such as diet and exercise. Unlike secondary hypertension, which is attributable to identifiable causes like chronic kidney disease or an endocrine disorder, primary hypertension does not have a clear medical cause but is a significant risk factor for various cardiovascular diseases.