Final answer:
A malar rash is most commonly associated with systemic lupus erythematosus (SLE). It is a symmetric erythematous rash that appears on the cheeks and bridge of the nose, resembling the shape of a butterfly.
Step-by-step explanation:
A malar rash is associated with several disease processes, but the most commonly associated disease is systemic lupus erythematosus (SLE). A malar rash, also known as a butterfly rash, is a symmetric erythematous rash that appears on the cheeks and bridge of the nose, resembling the shape of a butterfly. It is an important clinical feature of SLE and can be triggered or worsened by exposure to sunlight (photosensitivity).
Other diseases that may present with a malar rash include rosacea, dermatomyositis, and discoid lupus erythematosus. These conditions would need to be differentiated from SLE based on the patient's history, clinical findings, and laboratory tests.