This 3D animation by The Human Atlas explains Lupus. 

Normally, the body's immune system makes proteins called antibodies that protect it from illness. The antibodies attach themselves to harmful bacteria and viruses called antigens, which can cause illness.

Lupus is a chronic autoimmune disease, which means the immune system mistakenly attacks healthy body cells and tissues without the presence of antigens.

When this occurs, the antibodies are called autoantibodies. The result is inflammation and injury to cells and tissues that can lead to symptoms of lupus.

There are different types of lupus. Discoid lupus is usually limited to the skin; symptoms include a rash that appears as round red patches on the face, scalp, trunk or extremities. Usually, discoid lupus does not involve the body's internal organs, but the rash may be accompanied by joint aches.

Systemic lupus erythematosus (SLE) can affect any organ or organ system and most often results in episodes of inflammation in joints, tendons, and other connective tissues. Symptoms vary, such as fever, fatigue, weight loss, joint and muscle pain, swollen glands, hair loss, and nausea and vomiting; because there is such a range in symptoms the disease can often mimic other illnesses. The most characteristic symptom of SLE is a butterfly rash that appears on the cheeks and bridge of the nose. The symptoms can flare and remit over many years.

The causes of lupus are unknown although scientists believe that heredity and environmental factors are involved. This disorder is most common in women who are in their 20s and 30s. In some cases lupus may be induced by certain medications. Lupus is diagnosed with blood tests other diagnostic studies. It can be treated with medication according to the severity of the disease and symptoms.