Large-scale global retrospective study on the interaction between ancestry and risk of comorbid autoimmune diseases in patients with pemphigus

The pemphigus family of skin blistering diseases represents a rare yet potentially life-threatening condition characterized by multiple known genetic loci associated with other autoimmune disorders. While several studies have empirically indicated an increased risk of developing additional autoimmune diseases in individuals with pemphigus, the scarcity of data and the rarity of pemphigus have hindered efforts to establish and generalize these associations across diverse populations. In this study, we analyzed a dataset comprising 126 million patients, including 18,000 with pemphigus, to assess the likelihood of developing any of 74 autoimmune diseases following a diagnosis of pemphigus. For a subset of 26 diseases from this list with adequate patient numbers, we conducted further case-control retrospective analyses to quantify the odds and hazard ratios of developing comorbid conditions across various ethnicities. Our findings reveal highly significant and generalizable associations between pemphigus and pemphigoid diseases, discoid lupus erythematosus, lichen planus, and undifferentiated connective tissue disease, among others.