My best friend has this condition, it is also an auto-immune disorder and can sometimes overlap with Lupus. This condition presents with muscle weakness and a distinctive skin rash. Like Lupus, it is an inflammatory disease (myo" means "muscles" in Greek; "itis" means "inflamed." "Derma," means "skin). Also, like Lupus, this condition has periods of relapse and remission (the condition gets better or gets worse).
The most common signs and symptoms of dermatomyositis include:
1) A violet-colored or dusky red rash, most commonly on your face, eyelids, and areas around your nails, knuckles, elbows, knees, chest and back. Affected areas are typically more sensitive to sun exposure. The skin may become thick and hard in a way similar to scleroderma. When this happens, the condition is called sclerodermatomyositis.
2) Progressive muscle weakness, particularly in the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. This weakness is symmetrical, affecting both the left and right sides of your body.
The skin rash usually occurs at the same time as muscle weakness, but may precede muscle weakness by a few weeks. Weakness in muscles, such as your hips and shoulders, can lead to difficulty in getting out of chairs, climbing stairs, brushing your hair or working with your arms over your head. Weakness in your neck muscles can make it hard to hold your head up.
Other symptoms include: Difficulty swallowing (dysphagia), Muscle pain or tenderness, Fatigue, fever and weight loss, Hardened deposits of calcium under the skin (calcinosis), Gastrointestinal ulcers and infections, and
As you can see, all of these symptoms are very similar to the symptoms of Lupus. That is why it is SOOO difficult to diagnose auto-immune diseases and why your doctors could think that it's one auto-immune disease after test results, and then after other test results, feel that you have a different auto-immune disease. It is not that they don't know what they are doing (although this does happen), it is more that these diseases mimick each other so much and are so difficult to diagnose.
I wish you the very best and I do hope that you get some answers soon.
Peace and Blessings
Look For The Good and Praise It!