Malar erythema is a cutaneous eruption classically associated with autoimmune disorders such as acute cutaneous lupus erythematosus (ACLE), subacute cutaneous lupus erythematosus (SCLE), or dermatomyositis. However, malar erythema has many causes, including rosacea and other photosensitivity disorders such as polymorphous light eruption, phototoxic reaction, and photoallergic reaction. A clinical diagnosis is often suspected based on history and characteristic features seen on physical examination. For example, the classic “butterfly rash” of ACLE and SCLE typically follows sun exposure in a photodistribution, while a history of persistent flushing exacerbated by heat or foods favors a diagnosis of rosacea; likewise, pustules and papules have been reported as the most discriminating clinical finding suggesting a diagnosis other than cutaneous LE, as these are rare in rheumatic skin disease. ANA testing may be useful in the evaluation of a rheumatologic cause, as more than 95 % of ACLE patients and 80 % of SCLE patients will have significant ANA titers. Histopathology of the lesional skin can also aid in the differentiation of rheumatic diseases from nonrheumatic such as rosacea.