#1 is correct and natural. "to have hypertension" is a state. #2 is unnatural in the context of hypertension. "to have hypertension" is not an incomplete action. Normally, the present perfect refers to an ongoing state or a repeating action. Mrs. Ryan has been married since 2015. (ongoing state) Mrs. Ryan has baked cookies every Saturday since 2015. (repeating action). Normally, the present perfect refers to an ongoing action. Mrs. Ryan has been baking cookies since noon. (incomplete, ongoing action) There are other uses of the present perfect and the present perfect continous, but this brief answer just applies to the question about Mrs Ryan.

#1 is natural : Mrs Ryan first had symptoms or was diagnosed with hypertension in 2015. #2 is incorrect : you need to remove the word "having" and replace with a verb to match the "has been" structure. Dear Consultant at the hospital. May I introduce you to a patient of mine and refer her to your care, if you could arrange with your receptionist to book an appointment to see her. She needs to control her hypertension as soon as possible. The details are as follows. "Mrs Ryan has been suffering from hypertension since 2015" "I have been having severe problems controlling Mrs Ryan's hypertension since 2015" Please see her medical records and the treatment that as so far been tried. Your sincerely Dr x This is not a real letter, nor is it how it would be written, but I have included two sentences for people to discuss and disagree about the grammar. "Mrs Ryan has been suffering from hypertension since 2015" "I have been having severe problems controlling Mrs Ryan's hypertension since 2015" I have been having is okay in the second sentence but not in the first sentence.

Perfect focuses on the fact, perfect continuous focuses on the duration.

The first one has the nuance of a single event, or something static. While the second one has the nuance of a repeated event or something dynamic.

Another natural phrasing would be "Mrs. Ryan has been hypertensive since 2015"