U-M scientists find new genes linked to rheumatoid arthritis that are expressed differently in genetically identical twins Ann Arbor, Mich. -- They sleep together, eat together, and most people find it impossible to tell them apart. Identical twins who grow up together share just about everything, including their genes. But sometimes only one twin will have health problems when genetics predicts both of them should. Scientists at the University of Michigan Medical School are just beginning to understand how two people who are so similar biologically can be so different when it comes to the development of diseases like rheumatoid...