How is butterly skin rash defined?

Malar rash: A "butterfly rash" is also known as a malar rash. It is a red rash that occurs over the nasal bridge and extends onto the cheeks. It is called "butterfly" because it does resemble a butterfly in shape. It is one of the skin findings in patients with systemic lupus erythematosus.

Malar rash: A malar rash also called butterfly is a facial rash that is often seen in patients with lupus erythematosus, pellagra, dermatomyositis and bloom syndrome. 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.