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In medicine, malar rash (from Latin mala ‘jaw, cheek-bone’), also called butterfly rash, is a medical sign consisting of a characteristic form of facial rash. It is often seen in lupus erythematosus but is not pathognomonic - it is also seen in other diseases such as pellagra, dermatomyositis, and Bloom syndrome.
The malar rash of lupus is red or purplish and mildly scaly. Characteristically, it has the shape of a butterfly and involves the bridge of the nose. Notably, the rash spares the nasolabial folds of the face, which contributes to its characteristic appearance. It is usually macular with sharp edges and not itchy. The rash can be transient or progressive with involvement of other parts of the facial skin.
There are numerous other conditions which can cause rashes with a similar appearance. Where lupus is suspected further medical tests (usually an ANA as a screening test which is not specific for systemic lupus erythematosus) and a detailed history and examination are necessary to differentiate it from other conditions.