Autoimmune diseases and hematological malignancies: Exploring the underlying mechanisms from epidemiological evidence.

Autoimmune diseases are characterized by the irregular functioning of the immune system that leads to the loss of tolerance to self-antigens. The underlying nature of autoimmune diseases has led to speculation that the risk of malignancy might be higher or lower in patients with such diseases. However, the rarity and heterogeneity of both autoimmune diseases and malignancies is the main challenge for systematic exploration of associations between autoimmune diseases and cancer. The nationwide usages of electronic health records in Sweden and other countries has created longitudinal clinical datasets of large populations, which are ideal for quantifying the associations as well as possible guidance concerning the underlying mechanisms. In this report, we firstly summarize the population-based epidemiological association studies between autoimmune diseases and subsequent hematological malignancies using data derived mainly from Swedish nationwide data. These include over one million cancer cases and approximately 500,000 patients with medically diagnosed autoimmune disease. We further discuss the underlying mechanisms that contribute to the observed association between autoimmune diseases and hematological malignancies, including shared genetics, environmental factors, medical treatments of autoimmune diseases as well as dysregulated immune function.