Discoid lupus erythematosus is an autoimmune disease. When the disease manifests in multiple sites, it is classified as disseminated discoid lupus erythematosus. It is challenging for dermatologists to distinguish this condition from other erythematous diseases, and it is sometimes misdiagnosed as psoriasis. Dermoscopy and pathology biopsy are essential supplementary diagnostic tools. Furthermore, biologics utilized for psoriasis treatment may exacerbate the condition if incorrectly administered to patients with discoid lupus erythematosus. Herein, we present a case study in which disseminated discoid lupus erythematosus was misdiagnosed as psoriasis and worsened after the use of an interleukin-17 inhibitor known as secukinumab.