Subacute cutaneous lupus erythematosus: 25-year evolution of a prototypic subset (subphenotype) of lupus erythematosus defined by characteristic cutaneous, pathological, immunological, and genetic findings

Subacute cutaneous lupus erythematosus (SCLE) represents a widespread, photosensitive, nonscarring, nonindurated form of lupus erythematosus (LE)-specific skin disease. SCLE lesions are associated with a distinctive immunogenetic background including the production of Ro/SS-A autoantibodies. Individuals who have SCLE skin lesions as a component of their presenting illnesses represent a distinctive subset (subphenotype) of LE that enjoys a good prognosis with respect to life-threatening systemic manifestations of LE. SCLE skin lesions can be triggered by a number of different drugs the majority of which are capable of producing photosensitivity drug reactions in nonlupus patients. Single agent or combination aminoquinoline antimalarial therapy will suffice for 75% of SCLE patients. The remaining 25% will require other forms of systemic antiinflammatory therapy (e.g., diaminodipenylsulfone (Dapsone), thalidomide) or systemic immunosuppressive-immunomodulatory therapy. The etiopathogenesis of SCLE skin lesions is thought to result from four sequential stages: (1) inheritance of susceptibility genes (HLA 8.1 ancestral haplotype [C2, C4 deficiency, TNF-α-308A polymorphism], C1q deficiency); (2) loss of tolerance/induction of autoimmunity (ultraviolet light, photosensitizing drugs/chemicals, cigarette smoking, infection, psychological stress); (3) expansion/maturation of autoimmune responses (high levels of autoantibodies (Ro/SS-A), immune complexes, autoreactive T-cells); and (4) tissue injury/disease induction resulting from various autoimmune effector mechanisms (e.g., direct T cell-mediated cytotoxicity, antibody-dependent cell-mediated cytotoxicity).