It’s called an invisible disease by some and the great imitator by others. It’s lupus, and it is one painful, mysterious disease. 

May is National Lupus Awareness month, and while you may be aware of lupus, you probably know little about it unless it affects someone in your life directly. Lupus is rare and complex, and it can be frustrating— even devastating— to live with. Read on to learn more about this disorder.

1. Signs and symptoms are all over the place

As with many autoimmune disorders, symptoms of lupus come and go in repeated flare-ups or exacerbations. Symptoms of lupus— sometimes called SLE after its most common form, systemic lupus erythematosus— may range from mild to severe between flare-ups, and vary from patient to patient, according to the Lupus Foundation of America.

Considered to be a rheumatic disease, lupus is sometimes classified as a type of arthritis, but it is not limited to the joints. “Unfortunately, the signs and symptoms of systemic lupus are commonly vague, variable and nonspecific,” says Dr. Arta Bakshandeh, an internist and senior medical officer with Alignment Healthcare.

READ MORE: Lupus, Rheumatoid, and Other Types of Arthritis 

Those symptoms may include nausea, vomiting, fever, muscle aches and weight loss, says Bakshandeh. Because lupus symptoms are so varied, some patients ignore them until they become severe and cause internal damage. “When lupus affected my brain function, I finally realized that acceptance and openness was the key to recovery and sustained health,” says Elena Anciro, who was diagnosed with SLE in 2001 and blogs about it on her site Face Forward.

Perhaps the most intriguing thing about lupus symptoms, however, is what triggers them. Systemic lupus “can be flared by infections like mononucleosis,” Bakshandeh says.

One common trigger poses a particular challenge for lupus sufferers. “I think the most frustrating thing for patients with SLE is the need to avoid sunlight,” Bakshandeh says. “Several patients have expressed to me their sadness because they no longer go hiking or go out to the beach because the sunlight triggers their lupus.”

READ MORE: Reasons to Avoid Vitamin D Deficiency

2. It’s hard to diagnose

Because of its tendency to mimic symptoms of other illnesses, lupus is especially hard to diagnose. About 97 percent of people with lupus test positive for antinuclear antibodies, which destroy cells inside the body. However, some people without lupus also test positive for the antibodies, and this test alone cannot confirm a diagnosis.

There are other lab tests that can help doctors diagnose lupus, but there’s no single silver-bullet test. Doctors typically make a diagnosis from a combination of current symptoms, medical history, family medical history and lab tests. “Pregnancy can also cause lupus to flare and is often the first time a patient is diagnosed,” Bakshandeh says.

A diagnosis often follows “manifestations on the skin such as the butterfly rash, sensitivity to sun, lesions of mucous membranes such as the mouth, spotty hair loss” and others signs, Bakshandeh says. A butterfly, or malar, rash occurs in about 30 percent of lupus patients on the cheekbones and across the bridge of the nose, and is characterized by a blotchy, raised appearance.

3. There’s more than one kind of lupus

The most common type of lupus, SLE, affects the body’s major organs. “During a lupus flare, the body is essentially attacking itself, causing inflammation throughout the body,” Bakshandeh says.

SLE commonly attacks “areas like the skin, kidneys, heart, blood, joints and nerves,” he says. Lupus nephritis, or kidney damage caused by lupus flare-ups, affects up to 60 percent of lupus patients, according to the National Institutes of Health (NIH).

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Cutaneous lupus erythematosus is limited to the skin and is much less common than systemic lupus. People with cutaneous lupus develop raised, red, circular skin rashes. About 10 percent of cutaneous lupus patients develop systemic lupus, according to the LFA, but it is probable these patients already had systemic lupus, with the skin rash as their first symptom.

4. Sometimes lupus is temporary

The type of lupus that surprises people most often, Bakshandeh says, is drug-induced lupus. This syndrome displays symptoms similar to those of systemic lupus, but it’s caused by certain medications. Lupus symptoms go away a few months after discontinuing the drug, and damage to major organs is rare.

Hydralazine, a high blood pressure and hypertension medication, may be a culprit, as may procainamide, a drug for irregular heart rhythms. Less commonly, the tuberculosis drug isoniazid may cause drug-induced lupus.

And then there’s neonatal lupus, which is not a true form of lupus. It’s a rare condition in which the baby of a mother with lupus shows symptoms that mimic those of systemic lupus. The symptoms usually disappear before the baby is 1 year old, according to the Lupus Foundation. Most babies born to mothers with lupus are completely healthy.

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5. It affects minority women the most

Lupus has a typical onset between the ages of 15 and 44, and about 90 percent of lupus sufferers are women, according to the Lupus Research Institute. This is why lupus is commonly considered a disease of young women.

Black women are two to three times more likely to develop lupus than white women, according to LFA. “I just turned 20 when I received my lupus diagnosis, a time when life was supposed to begin,” says Anciro, who is of Filipino descent. “But instead I was enduring debilitating pain from joint and organ inflammation.”

Still, lupus of any type remains relatively rare: Only about 1.5 million, or less than half of one percent, of Americans have a lupus diagnosis.

Researchers are looking for clues to treat and cure lupus, including using drugs that currently treat other immune diseases. “The best way to manage lupus is to be followed regularly by a rheumatologist and [stay compliant] with medication,” Bakshandeh says.

Although the disease isn’t curable yet, Anciro agrees that it is manageable. “I’ve been major flare-free for six years and have slowly been able to accomplish the goals I had before I was diagnosed,” she says.

Her advice to the newly diagnosed is to face it head on, but to lean on friends, family or a support group when times get rough. “I’ve learned that if you ignore the emotional battle involved with having lupus, the physical battle will almost always be lost.”