Immune-mediated inflammatory diseases are a group of diseases characterized by generalized inflammation that results from immune dysregulation, especially involving the mechanisms of acquired immunity. These diseases may be familial, showing that genetic factors play an important role in their development. Additionally, the occurrence of one disease makes a patient prone to other diseases. However, the coexistence of systemic lupus erythematosus (SLE) and psoriasis (Ps) is very rare due to their distinct genetic determinants and mechanisms of pathogenesis. Treatment is also challenging, as medications used to treat one condition exacerbate or even trigger the symptoms of the other. This paper presents the case of a Ps patient with a family history of autoimmune diseases, who developed systemic lupus erythematosus during puberty, as well as a discussion on the coexistence of SLE and Ps in developmental age based on available literature searching for PubMed database and American College of Rheumatology and European League Against Rheumatism abstracts particularly in this subject.