I think skin biopsies are done when the doctor suspicions dermatomyositis, whereas muscle biopsies are done to check for polymyositis. Hope this helps.

Muscle biopsy will determine if its PM DM or IBM. Skin biopsy will help to diagnose DM. The inflammation can be seen on a MRI and will give the surgeon the best site for biopsy. There is no point in muscle biopsy if you have already started taking Prednisone as it interferes with the result. Hope this helps. Autumm

Hi bny806. I would see a neurologist. You want a comprehensive work-up so that the diagnosis is correct. You also will want to be placed on the most appropriate meds. A neurologist will run an EMG muscle test on your arms & legs. The muscle biopsy is important because it shows the pathology of the disease. Muscle biopsy distinguishes between DM, PM, and IBM. You will also find a full blood panel and autoantibody testing helpful. The autoantibodies will tell which organs are at risk for attack and the path the disease will most likely take in your body.

I have DM. In my third year with DM, I developed overlapping scleroderma. Scleroderma is a common DM overlap which may also involve skin issues. You may want to check out Sclero.org and see if symptoms look familiar to you on that site.

The Myositis Association website is a good place to learn more information about DM. I think the requirements for a myositis diagnosis have become more comprehensive.


I hope this helps.

thank you all so much!!! I have seen a few neuro's and am now at a university center (have been for 2 years now).. I have a rheumy there as well.. no one knows.. I've had multiple EMGs (all normal), epidermal nerve skin biopsy (showed severe small fiber neuropathy), LP's, blood work etc.... the rash I have had mildly (under my eye and on my eyelid) and now on my chest shoulders and back- everyone just says see a dermatologist as "skin" is out of their speciality, ugh everyone is so super specialized it's annoying! I am on IVIG, so Im sure that can interefere with results as well.. but I would assume if I'm symptomatic they should give some answers! I haven't had a muscle biopsy or skin biopsy to look at anything other than the epidermal nerve fibers

I believe a muscle biopsy would be helpful if you have muscle weakness. It will test abnormal activity in your muscle. The first step though would be an abnormal EMG. If your EMG is normal, then either they are testing the wrong muscle or you don't have muscle involvement (which can happen in DM).

A skin biopsy will allow them to do pathology on your rash to help further diagnose. Since I have PM and no rash, I'm not sure that process and if medications impact the result. My rookie thought is that it would not because the rash is present.

On a side note, I would question the IVIG for DM if you still have a rash. To me, that would indicate it isn't working the way we needed.

DM rash can be really stupborn and yes a skin biopsy helps some but also the look of the rash can be classic and not need much else. Rash can be hard to treat even with IVIG. Steroids helps mine the most.
You need a great medical dermatologist. The DM team at Stanford is great, i go there, but John hopkins and Mayo are also great.
Hope you can find some answers...

What is your biopsy comes back negative for DM but you have the rash that looks so like it and the mechanics hand and the holster rash. Can the biopsy be wrong? Should I see a rhuemy or nuero or take it as I do not have this?

Hi, cdtagcomcastnet, and welcome to this forum of nice people. Sometimes getting a diagnosis is difficult and takes a long time. For me, 2 neuros diagnosed me with PM based on symptoms in 2008. A few months after stabilizing me, they told me that I was a few weeks from death and didn't have time for a biopsy. They started me on prednisone immediately, which stabilized me, and ran a EMG/NCT (I call them the pin cushion tests). These showed "idiopathic inflammatory myopathy." A year later I fell and broke my leg, requiring surgery. At that time the surgeon did a muscle biopsy, which showed muscle damage but was inconclusive for PM or DM, probably because of all the prednisone I had taken. For about 6 months in 2010, I had rashes that wouldn't go away. A derma took skin biopsies of a couple affected areas and the diagnosis came back as overlapping DM and Lupus.

As for which type of doctor, some of us have rheumys and some have neuros. But you might want to start with a derma who will take skin biopsies, as that can often diagnose DM. Then if the skin biopsies show DM, you can decide on a rheumy or neuro at that time. Best wishes to you.