What to Know About Lupus, a Disease Affecting 1.5 Million Americans

— -- Singer Selena Gomez announced she will take a break from performing in order to care for her health, citing lupus as the main reason for taking time off of her world tour.

Since the 24-year-old publicly announced last year that she has lupus, a chronic autoimmune disorder, she has brought much-needed attention to the often misunderstood disease.

"I've discovered that anxiety, panic attacks and depression can be side effects of lupus, which can present their own challenges," the singer said in a statement to People on Tuesday, announcing she was taking a break.

Sandra C. Raymond, the president and CEO of the Lupus Foundation of America, said in a statement to ABC News today, “We applaud Selena Gomez for taking the time to take care of herself and highlighting this common, yet misunderstood aspect of coping with chronic illness.

“Life with lupus can be challenging. With symptoms that come and go, disease flares and remissions, and the uncertainty of what each day will bring, it’s normal to experience feelings of depression and anxiety,” Raymond added.

Here's what people should know about the disease that affects an estimated 1.5 million Americans and a total of 5 million people worldwide.

The chronic autoimmune disease can cause damage to any part of the body and cause a wide range of symptoms because it can affect so many different organs, a spokesperson for the Lupus Foundation of America told ABC News today.

Ninety percent of people diagnosed with the disease are women, and the disease is two to three times more prevalent among women of color, according to the foundation.

Symptoms of the disease include extreme fatigue, headaches, painful or swollen joints, fever, anemia, and a wide range of others that come and go during the course of the disease, according to the Lupus Foundation of America.

A butterfly rash across the across cheeks and nose is also a common and more specific symptom of lupus, a spokesperson for the foundation added, stressing that many symptoms of lupus also occur in other illnesses, which often makes a diagnosis difficult.

One major challenge for people with lupus is that it is a disease of flares, meaning one day someone can feel very healthy and not well at all the next day.

“People with lupus deal with flares when the disease is particularly active. When a lupus flare occurs, many people will notice a return of the symptoms they experienced previously or they may even develop new symptoms,” Raymond said.

Another struggle people with lupus face is that the disease is often not outwardly visible, causing it to be very misunderstood by the public.

Fifty percent of people with lupus cite emotional problems as the most difficult factor in coping with lupus, according to the Lupus Foundation of America.

“Lupus can be serious and life-threatening, although signs and symptoms of the disease are not always visible,” Raymond added.