This includes many diseases such as Systemic Lupus, Scleroderma, Sjogren's disease and Myositis but also conditions that cannot be classified easily:
As much as 25 percent of rheumatic disease patients with systemic symptoms cannot be definitively diagnosed. Furthermore, the majority of these patients will remain undiagnosed during 5 to 10 years of follow-up. Such patients were historically described as having "collagen" or "connective tissue" diseases, since they shared similar clinical and pathologic features of widespread inflammation. Increasingly, the term "systemic rheumatic" disease has replaced "collagen," "collagen-vascular," or "connective tissue" disease. This change reflects the recognition that these disorders probably represent perturbations of the immune system with resultant inflammatory tissue injury rather than primary disorders of collagen, vasculature, or connective tissue; the inciting events are not yet clear.
Systemic Lupus
Lupus is a systemic autoimmune disease that occurs when your body's immune system attacks your own tissues and organs. Inflammation caused by lupus can affect many different body systems — including your joints, skin, kidneys, blood cells, brain, heart and lungs.
Lupus can be difficult to diagnose because its signs and symptoms often mimic those of other ailments. The most distinctive sign of lupus — a facial rash that resembles the wings of a butterfly unfolding across both cheeks — occurs in many but not all cases of lupus.
Some people are born with a tendency toward developing lupus, which may be triggered by infections, certain drugs or even sunlight

