“In 2022, I was first diagnosed with Lupus SLE and then a rare T-cell lymphoproliferative disorder,” Halsey wrote. Lupus SLE, or systemic lupus erythematosus, is an autoimmune disease that can cause widespread inflammation and tissue damage in various parts of the body. The T-cell lymphoproliferative disorder is a rare condition involving the overproduction of T-cells, a type of white blood cell, which can lead to serious health complications.