have been diagnosed with PMR after more than a year

I am unaware of complications for untreated PMR.  what are they?

PMR causes a quite generalised state of inflammation in the body, especially in blood vessels. Over longer periods of time this can cause quite a lot of damage to the blood vessels and lead to a higher risk of cardiovascular disease: stroke and heart attacks in particular but also aortic aneurysm and peripheral vascular disease. Long term inflammatory states also have been implicated in the development of several cancers. 

It isn't a case of pred is bad, no pred is better - there is another elephant in the room. 

When you were diagnosed your GP should have made you aware of the symptoms of GCA which can occur in people with PMR.

EileenH has explained all the others, much better than I can, so please take notice.

Ooops - yes, sorry MrsK!

People who have PMR are at risk of developing GCA, which can lead to permanent loss of vision. About 1 in 6 patients who are being treated with pred do go on to develop the symptoms of GCA but usually are less likely to go blind. Patients who have PMR that is not treated with pred are more likely to develop GCA and are also probably less likely to recognise the symptoms: headache, jaw pain when chewing,  scalp pain, blurred vision, seeing double, dark patches in the visual field or a feeling there is a curtain in front of the eye. The only safe treatment to avoid going blind is pred - at a much higher dose than for PMR. So not taking pred for PMR may actually result in you needing far more pred in the end.

Fibromyalgia and PMR are very similar in that the desciption of the patient's symptoms include several things that are the same like widespread pain, fatigue, brain fog, joint stiffness and so on. This leads to confusion in diagnosis as there is no test for either and it is a clinical diagnosis - based on physical examination and history. However they are really quite different. In PMR the siffness and pain are mainly in the hips and shoulders (though that is not essential) and whilst in fibro the pain is all over, in PMR it tends to be more in the muscle groups that are affected and some bits don't hurt. Where a PMR patient has something more akin to GCA there will be claudication pain (in upper arms, thighs) on exercise and possibly a few other so-called GCA symptoms. 

The diagnosis of fibromyalgia used to be made on the prescence of a large number of paired tender spots - there are 9 pairs distributed all over the body and pressure on them causes exquisite pain. Whilst this may happen in PMR the points aren't always localised to a particular position. When I was first ill I had several places where I couldn't be touched without pain - some coincided with fibro spots so at first I was a bit confused, it could have been either.

The primary difference though is in the response to prednisolone. PMR symptoms respond to give a 70% improvement with a few days, not pain-free but very noticeably better. Pred has no effect on fibro pain at all. Fibro may respond to amitryptiline - PMR doesn't. This is because the causes of the pain are different. Although it isn't really know what the causes are, in fibro it seems there is something wrong with the nerve connections to and in the brain which cause problems processing pain. In PMR it is almost certainly an underlying autoimmune disorder which is causing vasculitis (inflamed blood vessels) causing swelling so the blood has difficulty getting through to the tissues. The pain is probably due to lack of oxygen supply - at rest it is often OK but on exercise the blood supply doesn't increase. If this happens in the upper body and into the head it can cause GCA, but the name PMR is just a description of the symptoms, they may appear in someone with GCA but in most patients it doesn't get so extreme and a lower dose of pred achieves good management of the symptoms.