Rheumatologists have long noted that women seem to be disproportionately affected by autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus (SLE). 
In fact, 80% of people who have autoimmune conditions are female.
However, exactly why this is the case has been something of a mystery.
New research which has been published in the journal Nature Immunology has shed some light on why women seem so vulnerable to these conditions.
It’s all in the genes. If you’re born female, the same genes express themselves in a rather different way than had you been born male.
Why has it take so long for researchers to stumble across this discovery? According to the senior author of the study, Johann Gudjonsson, who is Assistant Professor of Dermatology at the University of Michigan, medical researchers were previously focussing all of their efforts on hormonal differences.
"We found a completely new angle," he explains. "Our team identified a gene expression difference between the sexes that is associated with susceptibility to autoimmune disease."
These conditions happen when the body’s immune system attacks itself, becoming overactive. The body becomes overwhelmed by inflammatory proteins.
Inflammation is a process designed to protect the body and allow it to heal – but you can have too much of a good thing. Problems occur when there is too much inflammation, or it goes on for too long. These issues may lead to autoimmune disorders.
Why more women suffer from as rheumatoid arthritis
Dr Gudjonsson’s work revealed specific differences in how certain genes expressed themselves, depending on whether you’re a man or a woman.
Changes in sex hormones made no difference: "We found no evidence of involvement of oestrogen or testosterone in the immune differences we observed between women and men," says Dr Gudjonsson.
The study found that 661 genes were expressed differently between the sexes. Many of those genes had immune function, and overlapped with genetic pathways and risk genes, which are related to autoimmune diseases.
Skin samples of 82 healthy men and women who were free from autoimmune diseases were analysed by the researchers.
One protein, called VGLL3, was identified as a ‘master regulator’ of inflammation and autoimmunity. VGLL3 was only active in the skin samples of the healthy women – not the healthy men in the sample.
However, when the researchers looked at skin samples of men who had been diagnosed with autoimmune diseases, it was also activated, or ‘switched on’, in the same way as it is with women.
Hope for new treatments for autoimmune conditions
The University of Michigan researchers wrote in Nature Immunology, "This finding suggested that these sex-biased genes contributed to not only increased disease susceptibility but possibly also heightened disease activity. In this context, we note that being female is the strongest risk factor for the development of autoimmunity, and it dwarfs the identified autoimmune genetic risk variants."
Dr. Gudjonsson is hoping this new discovery will lead to new treatments; however, this will be years in the future.
The best new treatments for rheumatoid arthritis
So what can people who have autoimmune diseases do to ease their conditions at the moment? According to Consultant Rheumatologist Dr Stephanie Kaye-Barrett of 25 Harley Street there are many new treatments available in this area – especially for rheumatoid arthritis.
"The treatment for rheumatoid arthritis has transformed," she says. "Treatments that have been around for 50 years have been supplanted by new drugs called biological agents or anti-TNF drugs. These are injectable treatments which put the condition into remission."
Dr Stephanie Kaye-Barrett is optimistic about the new research been done in the area of rheumatology. "The drugs are getting better all the time," she says. "They’re becoming easier to administer, more effective and longer lasting. Things in the field are moving very fast — faster than most other specialities, which makes it very exciting."
Find out more about new treatments offered by rheumatologists. You can also discover how injections could help ease your arthritic pain.
