Lupus is an inflammatory disease that can involve many parts of the body, including the joints, skin, kidneys, blood, blood vessels, heart, lungs and nervous system. The condition can range from mild to life-threatening.

Lupus is an autoimmune disorder, meaning the body mistakenly attacks itself. The immune system helps protect the body by making antibodies, which are cells that attack foreign substances such as viruses and bacteria. Sometimes, however, this system malfunctions and creates abnormal autoantibodies that attack the body's own tissues. This causes inflammation, vasculitis (damage to blood vessels) and organ damage due to a buildup of immune system cells.

Like many autoimmune diseases, lupus is also categorized as a connective tissue disorder because of its effect on bone, cartilage and other connective tissues. About 10 percent of lupus patients have symptoms typical of other connective tissue diseases such as rheumatoid arthritis, myositis, scleroderma or Sjogren's syndrome, according to the American College of Rheumatology. Doctors sometimes refer to this as overlap syndrome or mixed connective tissue disease.

Estimates of the prevalence of lupus vary. The Lupus Foundation of America says there are at at least 1.5 million to 2 million Americans with lupus, most of whom have the most serious form, systemic lupus erythematosus (SLE) However, the Centers for Disease Control and Prevention (CDC) states that the number of Americans with SLE can be conservatively estimated at 322,000 to possibly more than 1 million.

SLE lasts the rest of a person’s life, typically with long periods of good health (remissions) interrupted by occasional exacerbations (flares). Lupus is not contagious, meaning it isn't spread from one person to another. There is no known cure or prevention, but there are many ways for people to cope with the condition, such as exercise, stress management, rest and getting educated about the disease. Much research is being conducted to improve the treatment of lupus, including improved diagnostic methods, new medications and a vaccine.

Ninety percent of lupus patients are women, according to the U.S. National Institutes of Health (NIH). The disease usually develops between ages 15 and 45. It can also develop during childhood and in middle and old age.

Lupus is more common and more severe in blacks, Asians, Hispanics and American Indians than in whites, probably because of genetics. Black women are three times more likely than white women to develop lupus, according to the CDC. Scientists have linked a gene to the higher risk of kidney disease in black patients with SLE.

About 15 percent of SLE patients develop the disease after age 55, according to the Lupus Foundation of America. This late-onset SLE is more common in whites, includes a slightly higher proportion of men than earlier-onset SLE and is typically milder and easier to manage.

Lupus varies greatly in how it affects people. Some individuals experience few problems, but others suffer one or more serious complications. Joint pain and stiffness are common, but unlike typical forms of arthritis, deformities seldom develop in the joints. Potential complications of SLE include:

• Osteoporosis. As with lupus, this common bone disease mostly affects women. Female lupus patients may have nearly five times the risk of a fracture from osteoporosis, according to the U.S. National Institutes of Health (NIH). Bone loss can result from corticosteroids used to treat lupus and from inactivity due to pain and fatigue caused by lupus.

• Pregnancy difficulties. Miscarriages are sometimes the first sign of SLE. Babies born to SLE patients may have heart, liver or skin conditions. A nationwide survey of more than 18 million American women found that SLE patients were more likely than other pregnant women to have a pregnancy-related death, require a Caesarean section or develop complications such as deep vein thrombosis (blood clot in a leg), sepsis (serious blood infection) or anemia (insufficient number of red blood cells). With proper medical care, however, most women with lupus can have a normal pregnancy and healthy baby, according to the NIH.

The American College of Rheumatology (ACR) suggests that SLE patients of childbearing age use birth control during flares and try to time pregnancies during periods of long remission. Recent studies indicate that SLE patients can safely take oral contraceptives, which were once thought to worsen the disease.

• Kidney damage. Inflammation of the kidneys can impair the ability to get rid of the waste products from the body effectively. Black patients are particularly prone to renal damage from lupus, researchers have found. Treating kidney disease early reduces the risk of chronic renal failure, which requires lifelong dialysis or a kidney transplant. Patients should ask their physician about regularly having a special urine test - not a routine urinalysis - for microalbuminuria (small amounts of protein in the urine), an early sign of kidney disease.
  
  
• Cardiovascular diseases. SLE damages the blood vessels, accelerates atherosclerosis (hardening and narrowing of the arteries) and can lead to stroke, heart attack or heart failure. A stroke is sometimes a symptom of SLE in an undiagnosed individual.
  
  
• Chest pain. Patients may suffer from pleurisy (inflammation of the membrane covering the lungs) or pericarditis (inflammation of the membrane covering the heart).
  
  
• Damage to the nervous system. SLE can cause a wide range of neurological disorders, including headaches, vision problems, seizures and mental disorders.

However, with regular physician visits and medication, most lupus patients do not develop serious health problems or have a shortened lifespan, according to the U.S. National Institute of Neurological Disorders and Stroke.