DEAR DR. ROACH: What is lupus, and what does it do to your body? I just had a friend diagnosed with it after many months of tests. — T.S.B.

ANSWER: The term “lupus” generally means systemic lupus erythematosis (SLE), which is a systemic disorder (as its name suggests). So, by definition, it affects multiple systems of the body.

One of the most commonly affected systems is the skin, and one particular localized disease of the skin — discoid lupus — is one of the conditions that helps make the diagnosis of SLE. I sometimes hear people with discoid lupus say they have “lupus,” but it is not the systemic disease unless other criteria are met. Other skin conditions seen in SLE include the classic “butterfly” rash on the face, marked sun sensitivity, mouth ulcers, and hair loss.

People with SLE commonly have systemic or “constitutional” symptoms such as fatigue, fever and generalized aching. The fatigue can be disabling. Weight loss is common in early SLE, but some people gain weight due to salt and water retention from the kidney manifestations of SLE or from treatment.

Joint problems (both pain and swelling) are present in over 90% of people with SLE. It is always more than one joint. Kidney problems with protein in the urine are common and a diagnostic criterion. Neurological disorders are infrequent but may include seizures, peripheral neuropathy, and acute confusion or psychosis.

The lining of the heart and lungs are often affected, which can be heard by an examiner, and an electrocardiogram shows typical changes. All of the blood cells — red, white and “blue” (platelets) — can be decreased.

Finally, there are blood proteins that are elevated in people with SLE. The ANA level is almost always high, but this is not a specific finding. I have seen more patients misdiagnosed with lupus because of a high ANA level (and no other criteria for SLE) than I have ever seen correctly diagnosed. The anti-Smith antibody is much more specific but not commonly seen, while the anti-double-stranded DNA test is more common and more specific than an ANA test. Blood tests alone do not diagnose SLE.

There are different scoring systems to make the diagnosis of definite and probable SLE using these criteria, but in clinical practice, the diagnosis is made using the judgment of an experienced clinician. In my practice, I refer all of my patients with suspected SLE to a rheumatologist.

The diagnosis of SLE isn’t completely straightforward and requires expertise, while the management of SLE requires a clinician who is both experienced and currently up-to-date in the medical treatment. This, again, usually means a rheumatologist.

Seventy years ago, prior to the development of steroids, the diagnosis of SLE used to be extremely dangerous, with half of the people who were newly diagnosed dying within five years — as bad as many cancers. Since steroids have many side effects and aren’t 100% effective, many new drugs have been developed, and most people diagnosed with SLE now can be well-managed.

However, it is still a serious, life-changing diagnosis that increases the risk of heart disease and cancer in addition to all the organ issues above. A general doctor working with the rheumatologist can recommend treatments to reduce your heart risk, as well as appropriate cancer screening tests.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu. (c) 2025 North America Syndicate Inc. All Rights Reserved