Lupus erythematosus usually refers to systemic lupus erythematosus (SLE), and there is no such thing as which is more severe, dermatomyositis or SLE. Both dermatomyositis and SLE have different levels of severity, and both can be life-threatening, so there is no such thing as a more serious outcome. Dermatomyositis is an autoimmune connective tissue disease involving the skin and striated muscle, with subacute and chronic onset. It usually includes both skin and muscle lesions, but can also manifest as a single lesion. When there is only simple skin and muscle damage, the condition is mild; however, when it involves respiratory muscle weakness, pulmonary infarction, pulmonary hemorrhage and tumors, it can be life-threatening, and then the condition is more serious. SLE is an autoimmune disease in which pathogenic autoantibodies and immune complexes are formed and mediate organ and tissue damage. Clinically, there is often multi-system involvement, and a variety of autoantibodies represented by antinuclear antibodies are present in the serum. When SLE patients only have skin and mucous membrane damage, such as erythema pteronyssinus, the condition is mild; when it involves multi-system damage, combined with lupus encephalopathy, lupus nephropathy and interstitial pneumonitis, the condition is more serious, and the severe cases can be fatal. Dermatomyositis and SLE have different degrees of severity, and both of them can be life-threatening when the condition is critical, therefore, there is no such thing as which one of them is more serious, i.e., dermatomyositis or SLE. If you have dermatomyositis and SLE and other related discomforts, it is recommended that you consult a doctor in a timely manner and follow the doctor’s instructions for standardized diagnosis and treatment.