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Systemic Lupus Erythematosus

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of Lupus.

Alternative Names

Corticosteroids; Immunosuppressant Drugs

Diagnosis

The first symptoms of SLE can resemble one of many syndromes or disorders, including rheumatoid arthritis, Still's disease, rheumatic fever, Lyme disease, multiple sclerosis, thrombotic thrombocytopenia purpura, cryoglobulinemia, Weber-Christian disease, viral infections, vasculitis, psychosis, and other conditions. Other autoimmune disorders, such as Sjogren's syndrome or scleroderma, may even be present as a co-condition. No single test can definitively confirm or rule out SLE and a number are required before SLE can be diagnosed definitively.

Criteria for Diagnosing System Lupus Erythematosus

1. Characteristic rash across the cheek

2. Discoid lesion rash

3. Photosensitivity

4. Oral ulcers

5. Arthritis

6. Inflammation of membranes in the lungs, the heart, or the abdomen

7. Evidence of kidney disease

8. Evidence of severe neurologic disease

9. Blood disorders, including low red and white blood cell and platelet counts

10. Immunologic abnormalities

11. Positive antinuclear antibody (ANA)

Note: Four of the criteria must be experienced by a patient before a classification of SLE can be made. These criteria, proposed by the American College of Rheumatology, are not to be relied upon solely for diagnosis, however.

Ruling out Other Conditions

The physician should first rule out common conditions that might be causing the symptoms. The physician may, for example, test the synovial fluid (the lubricating liquid surrounding joints) to rule out rheumatoid arthritis. Certain eye and saliva tests may be used if Sjgren's syndrome is suspected.

Some Conditions Resembling or Accompanying Systemic Lupus Erythematosus

Muscle, Joint, and Bone Disease:

Scleroderma (hardening of the skin caused by overproduction of collagen). Multiple sclerosis (fatigue, heaviness or clumsiness in the arms and legs). Rheumatoid arthritis (also an autoimmune disease and sometimes occurs with SLE.) Sjgren's syndrome (characterized by dry eyes and dry mouth). Mixed connective tissue disorder (very similar to SLE, but milder). Myositis (inflammation and degeneration of muscle tissues). Fibromyalgia. Lyme Disease.

Skin Diseases:

Rosacea (lesions are pus-filled blisters and do not atrophy). Seborrheic dermatitis (skin lesions on lips and nose). Lichen planus (affects mucous membranes). Leukoplakia (affects mucous membranes). Dermatomyositis (causes bluish-red skin eruptions in face and upper body, accompanied by swelling).

Lyme disease
Lyme disease is an acute inflammatory disease characterized by skin changes, joint inflammation and flu-like symptoms caused by the bacterium Borrelia burgdorferi transmitted by the bite of a deer tick. Symptoms resolve in 3 to 4 weeks even without treatment, but secondary or tertiary disease may develop if initial infection is not treated.
Dermatomyositis on the legs Click the icon to see an image of dermatomyositis.

Tests for Autoantibodies

Methods for measuring the antibodies involved with SLE vary and the range of results can be bewildering. Repeat tests may be needed.

Antinuclear Antibodies (ANAs). One test is used to detect antinuclear antibodies (ANA), which attack the cell nucleus.

High levels of ANA are found in more than 98% of SLE patients. A number of other conditions, however, also cause high levels of ANA, so a positive test is not a definite diagnosis for SLE:

  • Antinuclear antibodies may be strongly present in other autoimmune diseases (e.g., scleroderma, Sjgren's syndrome, or rheumatoid arthritis).
  • They also may be weakly present in about 20% to 40% of healthy women.
  • Some drugs can also produce positive antibody tests, including hydralazine, procainamide, isoniazid, and chlorpromazine.

A negative ANA test makes a diagnosis of SLE unlikely but not impossible. High or low concentrations of ANA also do not necessarily indicate the severity of the disease, since antibodies tend to come and go in SLE patients.

In general, the ANA test is considered a screening test:

  • If SLE symptoms are present and the ANA test is positive, other tests for SLE will be administered.
  • If SLE symptoms are not present and the test is positive, the physician will look for other causes, or the results will be ignored if the patient is feeling healthy.

ANA Subtypes. In some cases, physicians may test for specific ANA subtypes.

  • Anti-double stranded DNA (Anti-ds DNA) is usually found only in SLE patients. It may play an important role in injury to blood vessels found in SLE and high levels often indicate kidney involvement. Anti-ds DNA levels tend to fluctuate over time and may even disappear.
  • Anti-Sm antibodies are also usually found only with SLE. They are more constant and are more likely to be detected in African-American patients.
  • When the ANA is negative but the diagnosis is still strongly suspected a test for anti-Ro anti-La antibodies may identify patients with a rare condition called ANA negative, Ro lupus.

Antibodies to SR Proteins. An advance in diagnosing SLE has been the detection of antibodies to molecules called SR proteins, which are carried by most patients. The test accurately detects lupus in 50% to 70% of patients who test positive for these antibodies.

Antiphospholipid Antibodies. In SLE patients in whom blood abnormalities are suspected, tests will be administered to detect the presence of the two major antiphospholipid antibodies:

  • The test for the lupus anticoagulant antibody measures the time it takes blood to clot. A longer than normal blood clotting time indicates a higher chance for clotting in the body and, therefore, the presence of lupus anticoagulant.
  • An ELISA test (enzyme-linked immunosorbent assay) is performed to detect the anticardiolipin antibody.

As with the ANA, these antibodies also have a tendency to appear and disappear in a single patient. Patients who have these autoantibodies as well as blood clotting problems or frequent miscarriage are diagnosed with antiphospholipid syndrome (APS), which often occurs in SLE but can also develop independently.

Miscellaneous Blood Tests

Complement. Blood tests of SLE patients often show low levels of serum complement, a protein in the blood that aids the body's infection fighters. Individual proteins are termed by the letter "C" followed by a number; common complement tests measure C3, C4, C1q, and CH50. There is some evidence that complete deficiencies of C1q may be a key factor in the inability of the immune system to contain the autoimmunity process. Complement levels are especially low if there is kidney involvement or other disease activity.

LE Cell Tests. The first blood test ever used for SLE called LE (lupus erythematosus) cell test is positive in only about half of patients with SLE and is not used often now.

Blood Count. White and red blood cell and platelet counts are usually lower than normal and depending on severity are used to determine complications, such as anemia or infection.

Formed elements of blood Click the icon to see an image of the formed elements of blood.

Skin Tests

If a skin rash is present, the physician may take a biopsy (a tissue sample) from the margin of a skin lesion. A test known as a lupus band detects antibodies known as immunoglobulin G (IgG), which are located just below the outer layer of the tissue sample. They are present in about 80% of patients with active SLE and in between 30% and 40% of those with inactive disease. The biopsy will not differentiate between systemic and discoid lupus, but it can rule out other diseases. Tests for other antibodies will rule out or confirm discoid lupus and subacute cutaneous lupus.

Tests for Serious Complications of SLE

Kidney Damage and Lupus Nephritis. Kidney damage in patients already diagnosed with SLE may be detected from the following tests:

  • Blood tests that measure creatinine, a protein metabolized in muscles and excreted in the urine. High levels suggest kidney damage, although it can also be present with normal creative levels.
  • Tests for detecting anti-ds DNA antibodies and complement. High levels of anti-ds DNA and low levels of complement C3 suggest kidney damage. (It should be noted, however, that some patients with severe kidney damage show low levels of anti-ds DNA.) Testing for anti-C1q antibodies now appears to be an even more reliable indicator of lupus nephritis.
  • Urine analyses. They should be performed at four- to six- month intervals to check for signs of kidney involvement.
  • A kidney biopsy. This may be performed to determine if lupus nephritis is present when less invasive tests indicate kidney involvement. It is not absolutely accurate but it helps determine treatment. Electron microscopy (very high-powered electronic microscopes) may be especially important in obtaining critical information on the degree of kidney damage.

Lung and Heart Involvement. A chest x-ray may be performed to check lung and heart function. An electrocardiogram and an echocardiogram are administered if heart disease is suspected.

ECG Click the icon to see an image of an electrocardiogram.

Central Nervous System Complications. SLE occurring in the central nervous system (CNS) can be difficult to diagnose because its symptoms are easily confused with other psychiatric and neurologic conditions.

  • Tests of the cerebrospinal fluid (CSF) for elevated levels of autoantibodies are the most reliable ways to detect CNS complications caused by a faulty immune system.
  • Additional tests, including electroencephalograms (EEGs), magnetic resonance imaging (MRI), computed tomography (CT), or x-rays may be useful when blood vessel blockage in the brain is suspected.
  • If the physician suspects that CNS symptoms are caused by infection, especially for patients who are receiving immunosuppressant therapy, a lumbar puncture should be performed.

Osteoporosis. To detect early osteoporosis in SLE patients whose disease has lasted more than 3.5 years, experts recommend an imaging test called dual energy x-ray absorptiometry (DEXA) to measure bone mineral density.

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