Pemphigus is a group of rare life-threatening autoimmune diseases mainly affecting skin and mucosa. It contains two subtypes: pemphigus vulgaris (PV) and pemphigus foliaceous (PF). Its pathogenetic process is attributed to abnormal immune system activation, especially humoral immune which produces specific autoantibodies against epithelial adhesion structures such as desmoglein 1 (Dsg 1) and desmoglein 3 (Dsg 3) [1]. According to the latest research, the pooled incidence rate of pemphigus vulgaris was 2.83 per million person-years [2].

Since 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes Coronavirus Disease 2019 (COVID-19) has brought an enormous burden to the medical community. It’s known that viral infections can stimulate the development and aggravation of autoimmune disease [3], and cases of new-onset or aggravation of bullous pemphigoid, pemphigus foliaceous, and pemphigus vulgaris have been described [4], [5], [6]. Moreover, Systemic corticosteroids like prednisone are still the mainstay and first-line treatment of pemphigus. However, in some moderate-to-severe cases, other oral immunosuppressants like azathioprine and methotrexate are added [7]. Under the circumstances, the escalating possibility of SARS-CoV-2 infection among pemphigus patients with weakened immune systems caused by long-term glucocorticoids or immunosuppressants posed a significant concern for both patients and dermatologists. In addition, how to adjust the dose of glucocorticoids and whether to continue using the immunosuppressants for these SARS-CoV-2 infected pemphigus patients also present difficulties for dermatologists. Nowadays, no consensus has been reached on the optimal management of SARS-CoV-2 infection in pemphigus patients [8], [9], [10], and the clinical evidence about the association of these two diseases based on real-world research is also still insufficient. Based on extrapolations of pre-clinical data, early dermatological guidelines suggested that during COVID-19 symptoms, immunosuppressants such as azathioprine, mycophenolate, cyclophosphamide, methotrexate, and cyclosporine should be gradually reduced to the lowest effective dose [11]. Contrary to previous guidelines, recent clinical data suggests immunomodulatory drugs may reduce adverse outcomes from COVID-19 co-infection, indicating a need for further research. Omicron strain now is the dominant virus type affecting globally [12], the rapid and widespread of Omicron in China also suggests the necessity to perform related studies to investigate the characteristics of COVID-19 in the pemphigus population.

Based above, a study to investigate the association between pemphigus patients treated with immunosuppressants, especially low-to-medium dose glucocorticoids, and SARS-CoV-2 infection was conducted at the dermatology department of West China Hospital. It is hoped that this study could provide a reference for the clinical management of pemphigus patients during the COVID-19 period to some extent.