RecruitingPhase 2Drug trialSafety of Tofacitinib, an Oral Janus Kinase Inhibitor, in Primary Sjogren DiseaseBackground: Sjogren disease is an autoimmune disease - that is, a disease that causes the body's immune system to attack its own organs and tissues. Sjogren disease can affect the kidneys, lungs, or other organs. It can also cause dry mouth and eyes, fever, joint pain, rashes, and other symptoms. Researchers want to know if a drug approved to treat rheumatoid arthritis and other autoimmune diseases can help people with Sjogren disease. Objective: To test a drug (tofacitinib) in people with Sjogren disease. Eligibility: People aged 18 to 75 years with Sjogren disease. They must be enrolled in protocol 15-D-0051. Design: * Participants will be screened. They will have a physical exam with blood and urine tests. They will give samples of saliva; a small sample of tissue will be taken from a salivary gland. They will have a test of their heart function. They will have an eye exam, including a test for dry eyes. * Tofacitinib is a tablet taken by mouth. Participants will take the drug twice a day at home. * Participants will have 9 clinic visits over 28 weeks. Each visit will take up to 5 hours. In addition to repeated tests, they will have tests of the speed and pressure of blood flow through their body. They will complete health questionnaires throughout the study. * Participants will also have 5 phone visits during the study. They will review their health and study treatments. * They will have 1 final visit after they stop taking the drug.