PDCD1 and COVID-19: To better understand the interaction between sarcoidosis and COVID-19 in terms of clinical manifestations, treatment, and pathogenesis, this study discusses how the two diseases might involve some common mechanistic immune responses, including RAS in pulmonary and some cell death pathways around the regulation of autophagy, apoptosis, and programmed cell death (PD-1/PD-L1 axis) (Figure 1).