Lupus can be tricky to diagnose, so consult a doctor if you think you might have symptoms.
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What is lupus?
Lupus is short for a condition called systemic lupus erythematosus (SLE). It’s an autoimmune disease that can take years to diagnose because the symptoms can masquerade as other illnesses.
Lupus isn't rarearound 1.5 million Americans, mostly women, are affected. But lupus can be misdiagnosed as rheumatoid arthritis or another condition. And symptoms that seem like lupus can sometimes be due to a virus.
The American College of Rheumatology says that if a patient has at least 4 of these 11 signs (though not necessarily all at the same time) they can be diagnosed with lupus.
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A persistent rash across the cheeks and nose, in the general shape of a butterfly, is "very characteristic" of lupus, says Dr. Gary Gilkeson, MD, a professor of medicine at the Medical University of South Carolina in Charleston.
While about 30% of lupus patients typically get this rash, it can also be due to rosacea or other skin conditions, and this symptom alone is not enough to make a diagnosis of lupus.
Exposure to sunlight or other sources of ultraviolet light (even artificial) can worsen a lupus patient’s butterfly rash. It can also trigger sores on other parts of the body, usually on sun-exposed areas, and lead to joint pain and fatigue. Fair-skinned patients tend to be most affected.
However, Dr. Gilkeson warns that this symptom can be overused in diagnosis: "It is a confusing one," he says. "A lot of people say that they are sun-sensitive."
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Mouth or nasal sores
Mouth ulcers are one of the most common symptoms of lupus. But what makes a lupus mouth ulcer unique, says Dr. Gilkeson, is that it usually comes pain-free. And rather than developing on the sides of the mouth or gums, these sores typically reside on the roof of the mouth. Lupus-related ulcers can also appear inside the nose.
Joints that are red, warm, tender, and swollen may signal lupus. Aching and stiffness alone aren’t enough; the joints have to be affected by arthritis and these other "cardinal signs of inflammation," says Michael Belmont, MD, director of the lupus clinic at Bellevue Hospital and medical director at the New York University Hospital for Joint Diseases in New York City.
Dr. Belmont notes that at least two joints, typically smaller ones, have to be persistently affected for at least six weeks for the symptom to qualify as one of the four diagnostics.
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Inflammation of the lining of the heart or lung
Inflammation of the lining around the heart (pericarditis) or lungs (pleuritis) can be a sign of lupus. But both conditions are more commonly due to viral illnesses, says Dr. Belmont.
Even though the inflammation rarely affects the functioning of either the heart or lungs, it can cause sharp chest painespecially when a person is coughing or taking a deep breathand may occasionally spark shortness of breath.
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Microscopic blood cells and proteins that are not normally found in urine can appear in the urine samples of some lupus patients. Yet again, a lot of other illnesses can be to blame, including urinary tract infections and kidney stones.
A healthy kidney filters proteins out of the blood as it creates urine, explains Dr. Belmont. But if the kidney is inflamed and not functioning properly, as can be the case with lupus, proteins may sneak into the urine.
These abnormalities don’t usually cause symptoms. However, if the loss of protein (specifically albumin) is substantial, the feet may swell. And if someone has progressed to kidney failure, he or she might have some nausea and weakness.
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Seizures or psychosis
Lupus can trigger a variety of brain and nervous system problems, including nonspecific symptoms like anxiety, headaches, and vision problems. However, two additional concrete symptoms make the list: seizures and psychosis, which is a break from reality and can include delusions and hallucinations.
For less specific symptoms like headaches, it can be difficult to tease apart whether they are caused by lupus, the medications used to treat it, or the stress of living with the disease.
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Anemia, or an inadequate number of circulating red blood cells, is very common, especially in lupus’s target population: women. Iron deficiency anemia, for example, is frequently present during menstrual cycles. More specific to lupus, however, is a disorder called hemolytic anemia.
"It’s not just a low blood count. The condition is actively destroying the cells," explains Dr. Gilkeson, adding that certain lab tests can tell the types apart.
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A discoid rash is "fairly classic" in lupus, says Dr. Gilkeson. The disc-shaped patches appear red and raised, and typically develop on the face, scalp, and neck. They often leave scars.
The antinuclear antibody (ANA) test is the go-to screening test for lupus. If the result is negative, says Dr. Gilkeson, you can "almost guarantee" that a patient doesn’t have lupus. On the other hand, a positive result is much less clear; 90% to 95% of people who have a positive ANA test don’t have lupus.
ANAs are proteins made by the body that can attach to DNA and other substances inside cells. But just because they are present in the body doesn’t necessarily mean they will attack these substances. These antibodies are found in at least 5% of the general population, so there are "many more people walking around with ANAs who are perfectly healthy or have some illness that has nothing to do with lupus," adds Dr. Belmont.
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Other antibody tests
To unravel which people with positive ANA tests actually have lupus, additional blood work can be done. Doctors look for other potentially troublesome antibodies, so they will test for anti-double-stranded DNA and anti-Smith antibodies. These tests are less likely to be positive unless a patient truly has lupus. However, a person who has negative test results could still have lupus, even though this is not so in the case of ANA tests.
"These confirmatory antibodies are very critical to the accuracy and reliability of the diagnosis," says Dr. Belmont. The series of tests, combined with the ANA, he adds, will usually provide a fairly reliable answer.