What is myositis, the condition Samantha Ruth Prabhu is being treated for

Samantha said her doctors expect her to recover soon. (Image credit: Instagram)

Actor Samantha Ruth Prabhu has opened up about her struggle with an autoimmune condition called myositis. She posted the health update on Instagram today, which led to an outpouring of support for her.

"The doctors are confident that I will make a complete recovery very soon," she told her followers, while also also acknowledging "the bad days".

Myositis is essentially a general inflammation of the muscle, caused when the immune system becomes "misdirected" and starts attacking the body's healthy tissue, according to the US-based Myositis Association.

It is a rare disorder that shows up in several forms. Its symptoms, swelling weakness and muscle damage, show up slowly.

Much before the condition is diagnosed, patients may experience trouble moving, clutching objects and swallowing.

Myositis' causes are unclear. But experts believe certain individuals have predisposing genes, which can be triggered by infections or toxins.

There are several treatments available for Myositis -- biologic therapies, physiotherapy and steroids, among others. But it cannot be cured.

Most patients of myositis respond to treatments involving steroids, immunosuppressive therapy and exercise, according to the UK's National Health Service.

If left untreated or not treated effectively, myositis can lead to significant disability and can even be fatal.