One of my secondary conditions I occasionally get is called vasculitis. It is not unusual to get this with an autoimmune disease. There are many different types, but over all it is the inflammation of blood vessels. A good reference website is vasculitis foundation. Here is info on the type of vasculitis I was diagnosed with 2 years ago.
Henoch-Schönlein purpura (HSP) is a systemic vasculitis that causes the blood vessels in the skin to become inflamed, causing red spots. When the blood vessels in the skin get inflamed, they can bleed, causing a rash that is called purpura. This rash is typically seen on the lower legs or arms. The specific skin lesion is characterized by the tissue deposition of an immune system product, called IgA immunoglobulin, which is also found in kidneys of patients with a renal disease, called IgA nephropathy.
HSP occurs more often in children than in adults, and many cases follow an upper respiratory tract infection (infection in your sinuses and /or lungs). Half of affected children are under age five, although kidney involvement is more likely to be severe in older children. Compared to children, adults had more severe and frequent kidney involvement.
The first time I had this I was at work and kept thinking I had a never ending charlie horse in my legs. I finally pulled up my pants and saw the rash occurring. My co-worker's father had this one time and recognized it. I had 2 skin biopsies done to confirm. One was on my leg and the other on my belly. I have had a few mild outbreaks with it since then. (2 years ago) The worst was that first 2 months it happened. I am in remission with it, but if I can get a flare up anytime. It is normally treated with prednisone or another immune suppressant drug.
A more recent post on a new diagnosis of vasculitis.