Autoimmune Questions

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One of my sisters had a physician question her recently about a family history of autoimmune disease. She herself has no autoimmune issues, but asked me if Sjogren's and other autoimmune diseases are inherited. 

That's a good question. Here's what that Johns Hopkins Medical Institution says on a frequently asked question site: 

Q: Are autoimmune diseases inherited?

A: Clinical and epidemiologic evidence as well as data from experimental animals demonstrate that a tendency to develop autoimmune disease is inherited. This tendency may be large or small depending on the disease but, in general, close relatives are more likely to develop the same or a related autoimmune disease. A number or genes have been implicated in causing autoimmune disease, primarily genes related to the human major histocompatibility complex called HLA. 

Q: If autoimmune diseases are not primarily inherited, what causes them?

A: It seems likely that environmental factors acting with the genetic predisposition of the patient are responsible for triggering autoimmune disease. A few such triggers have been identified, including a number of drugs that are associated with some forms of lupus, thrombocytopenia, hemolytic anemia and other autoimmune disorders. Infections can be followed by an autoimmune disease in a few instances such as rheumatic fever followed by a streptococcal infection and Guillain-Barre` syndrome caused by chlamydia. A great deal of circumstantial evidence suggests that viruses may play a role in initiating some autoimmune diseases. A number of nutrients have been studied including iodine which contribute to the onset of autoimmune thyroid disease. In most cases, however, we do not have clear evidence of a particular environmental trigger of autoimmune disease.

Another good question: Are autoimmune diseases contagious? The short answer is no. The long answer is here: 

Autoimmune diseases are not normally contagious.You cannot catch an autoimmune disease from another person like you can a virus or bacteria. Autoimmune diseases are not contagious by sex or by blood. The only known transfer of autoimmunity occurs between mother and fetus during pregnancy, and is still rare even in affected mothers.

Even autoimmune diseases caused by white blood cells do not seem to be contagious by shared needles, blood transfusion or organ transplant. Although we are unaware of direct research on this issue, what may happen is that the number of white blood cells transferred by these methods is relatively small. The normal white blood cells and other normal immune controls presumably neutralize any disease-causing properties of the autoimmune person's white blood cells.