What causes the butterfly rash in systemic lupus erythematosus?

The exact cause of the butterfly rash in systemic lupus erythematosus (SLE) is not fully understood, but several factors are believed to contribute to its development:

Immune system dysfunction: In SLE, the immune system mistakenly attacks the body's own tissues, leading to inflammation and tissue damage. This immune dysregulation can affect the skin, causing the development of various skin lesions, including the butterfly rash.

Vasculitis: Vasculitis, or inflammation of the blood vessels, is a common feature of SLE. It can affect small vessels in the skin, leading to the development of red, scaly patches that can spread and merge to form the characteristic butterfly-shaped rash.

Sun exposure: Ultraviolet (UV) radiation from sunlight can trigger or worsen the butterfly rash in SLE. UV radiation can induce skin inflammation and activate the immune system, leading to the development of skin lesions.

Hormonal factors: SLE is more common in women, and hormonal changes, particularly those related to estrogen, are thought to play a role in the development and severity of the butterfly rash.

Genetic factors: Genetic susceptibility is also considered a contributing factor to SLE and the development of the butterfly rash. Certain genetic variations have been associated with an increased risk of developing SLE and may influence the severity and characteristics of the rash.

It's important to note that the butterfly rash is not the only skin manifestation of SLE. Other skin lesions that can occur in SLE include discoid lupus erythematosus, photosensitivity, oral ulcers, and various types of rashes.