By Robert Bazell, NBC News Chief science correspondent
With the third part of our series, "Medical Mysteries," about auto- immune diseases, we turn to what many see as the biggest mystery of all: why do these disease strike women in far greater proportions than men?
As many have you have commented in response to earlier reports and blog postings, all these diseases do indeed affect men as well and we certainly do not mean to ignore that fact. But still, it is overwhelmingly a problem for women. The numbers vary for different diseases, but they can range from three to 10 times as common in women as compared to men.
So what is the answer? The fact is that scientists do not know--even though they have been searching for years. Clearly, a woman has to have a difference in her immune system so she can tolerate a fetus in her body. Clearly, hormones are involved, because often auto-immune diseases get getter or worse before, during, and after pregnancy and menopause. Many scientists think that if they could understand why women suffer disproportionately, they would find better treatments.