Systemic lupus erythematosus:

Systemic lupus erythematosus (SLE) is a disease of unknown etiology in which tissues and cells are damaged by pathogenic autoantibodies and immune complexes. The abnormal immune responses include (1) polyclonal and antigen-specific T and B lymphocyte hyperactivity, and (2) inadequate regulation of that hyperactivity. At onset, SLE may involve only one organ system (additional manifestations occur later) or may be multisystemic. The malar ("butterfly") rash is a photosensitive, fixed erythematous rash, flat or raised, over the cheeks and bridge of the nose, often involving the chin and ears.