Malar rash\

The malar rash is one of the most recognizable cutaneous manifestations of SLE and is part of the SLICC and ACR classification criteria for the disease. Pathophysiologically, it results from immune complex deposition at the dermal-epidermal junction and UV-induced keratinocyte apoptosis, which exposes nuclear antigens and triggers local inflammation (type III hypersensitivity). The rash classically spares the nasolabial folds, distinguishing it from rosacea, which does not spare these folds and often has telangiectasias and papulopustules. Malar rash is typically photosensitive, worsening with sun exposure, and may be accompanied by other lupus-specific skin findings such as discoid lesions or subacute cutaneous lupus. Clinically, SLE patients may also have systemic features including arthritis, serositis, renal involvement (lupus nephritis), hematologic abnormalities (cytopenias), and positive autoantibodies (ANA, anti-dsDNA, anti-Smith). On histology, skin biopsy may show vacuolar interface dermatitis and a positive lupus band test (immunoglobulin deposition at the dermoepidermal junction) via immunofluorescence. Differentiating malar rash from other facial erythemas (rosacea, seborrheic dermatitis, dermatomyositis's heliotrope rash) is a common board question—dermatomyositis's heliotrope rash involves periorbital violaceous discoloration with edema and Gottron papules on the knuckles, not nasolabial fold sparing.