The appearance of erythema can be caused by a variety of diseases, and in the case of SLE, this condition is an immune disease. Erythema is caused by a generalized or limited expansion of the capillary network in the papillary layer of the dermis, which may appear discoid in the early stages and gradually increase in size and spread in later stages, causing systemic vascular lesions in severe cases. It can also cause lesions in multiple organs, such as the kidneys and heart, and can manifest as lupus nephritis and pericarditis, requiring active immune intervention therapy, which is usually commonly treated with hormone therapy. In addition to SLE, it can also be seen in conditions such as eczema and ringworm, which require a visit to a dermatologist for an examination to clarify the specific type and then select a targeted treatment plan.