Another Possible Underlying Mechanism for the Positive Association Between Celiac Disease and Systemic Lupus Erythematosus: The Role of Interleukin 21

To the Editor: We read with great interest the recent contribution by Ludvigsson, et al 1. They reported the increased risk of systemic lupus erythematosus (SLE) in 29,000 patients with biopsy-verified celiac disease (CD) and suggested that the association of CD and SLE could be part of the spectrum of “shared autoimmunity.” We would like to add another pathomechanism of the association between the 2 diseases. SLE is a complex autoimmune disease characterized by dysregulated interactions between autoreactive … Address correspondence to Dr. J.I. Shin, Department of Pediatrics, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, CPO Box 8044, Seoul 120-752, Republic of Korea. E-mail: shinji{at}yuhs.ac