Autoimmune diseases can be tricky to diagnose because they often share similar symptoms. For example, psoriasis and lupus are two types of autoimmune diseases that can cause skin symptoms.

Up to 85 percent of people with lupus have some type of skin symptom. Sometimes, the skin and joint symptoms of lupus can look like psoriasis, and psoriasis symptoms may look like lupus.

Understanding the skin symptoms associated with each condition can help you tell them apart and get the appropriate treatment.

Who Gets Psoriasis vs. Lupus?

Psoriasis is more common than lupus in the United States. More than 8 million adults have psoriasis, while about 1.5 million people have lupus. About 10 percent of people with lupus have a type limited to the skin, called cutaneous lupus erythematosus.

Both psoriasis and lupus affect people of different genders, races, and ethnicities. Although psoriasis is equally common in men and women, about 90 percent of those with lupus are women, according to the Lupus Foundation of America.

Psoriasis is most common in non-Hispanic white people. Lupus is less common in white women than in African American, Hispanic, Native American, Asian American, Native Hawaiian, and Pacific Islander women.

Both conditions can develop at any age. Psoriasis is most often diagnosed between the ages of 20 and 30 or 50 and 60, while lupus is usually diagnosed between ages 15 and 44.

One study found that psoriasis and psoriatic arthritis (arthritis that affects the joints) were more common in people with lupus than in the general population. Lupus-related rashes also developed more often in people with psoriasis.

Can You Have Both Lupus and Psoriasis?

It’s possible for one person to have both psoriasis and lupus. But even though it does happen, it’s uncommon for these conditions to co-occur.

If you have both lupus and psoriasis, it’s important for your doctor to know about both diagnoses. Your healthcare team can weigh the pros and cons of different therapies so the treatment for one condition doesn’t make the other one worse.

What Causes Psoriasis and Lupus?

Scientists don’t know the exact reason why some people develop psoriasis or lupus. Both are caused by the immune system attacking its own tissues. If your immune system attacks your skin cells in either disease, you may see a skin rash.

In psoriasis, white blood cells called T cells become overactive. They then cause inflammation in the skin and joints. In lupus, inflammation involves many different immune cells, including T cells, B cells, and neutrophils (a type of white blood cell) that can attack multiple organs.

What Does Psoriasis Look Like?

Psoriasis can appear on any part of the body. Psoriasis symptoms can appear in unique ways in different people. Common symptoms include patches of thick, dry, scaly skin that can look red, brown, or purple, depending on your skin tone. These patches are also often covered in a silvery coating called scale.

The type of psoriasis also affects how psoriasis looks, and there are five main types:

• Plaque psoriasis (also called psoriasis vulgaris) is the most common type of psoriasis. This type looks like red or purple patches of thick, scaly skin that can appear anywhere on the body.
• Inverse psoriasis appears as a red or darker patch of smooth, irritated skin in the skin folds, such as the underarms, breasts, genital area, or buttocks.
• Guttate psoriasis appears as small, round spots of inflammation that are red or darker than the surrounding skin. It can appear on any part of the body — usually the arms, legs, chest, or back.
• Pustular psoriasis looks like small, pus-filled bumps commonly seen on the hands or feet.
• Erythrodermic psoriasis is a rare and life-threatening type of psoriasis involving large areas of red or discolored skin. It also causes pain, fever, dehydration, and changes in heart rate.

Beyond Skin: Nail and Joint Psoriasis

Psoriasis can affect more than your skin. Psoriasis can also affect nails, a condition known as nail psoriasis. This can cause the nails to thicken, change color, and develop pits or ridges. In severe cases, the nail can even separate from the nail bed or fall off entirely.

Psoriatic arthritis can cause joint pain, swelling, and stiffness, which can affect one or more joints in the body, including the fingers, toes, spine, and pelvis. In addition to joint symptoms, psoriatic arthritis can also cause fatigue, eye inflammation, and changes to the nails, such as pitting, thickening, or separation from the nail bed.

What Does Lupus Look Like?

Lupus can affect the skin on any part of the body. Lupus rashes are most common in areas of the skin that can be exposed to the sun, such as the face, arms, legs, and shoulders. Many of the symptoms of lupus and psoriasis are similar.

Lupus rashes are classified based on three types of cutaneous lupus: acute cutaneous lupus (ACL), subacute cutaneous lupus erythematosus (SCLE), and chronic cutaneous lupus.

Acute Cutaneous Lupus Erythematosis

Symptoms of ACLE can appear when lupus is active. They may go away when lupus is under control.

A malar rash is the most recognizable sign of lupus. This is a butterfly-shaped rash that appears on the face, stretching across the nose and cheeks. However, it usually doesn’t affect other parts of the face, such as the nasolabial folds (area between your lips and nose). If you have a malar rash, you may look like you’re blushing in mild cases. In severe cases, it can be very discolored and itchy.

If the rash appears on other parts of the body, such as the arms or legs, it’s called a maculopapular rash of lupus or photosensitive lupus dermatitis. It may look like an allergic reaction.

Malar rashes usually come and go and don’t tend to lead to scarring or permanent discoloration. They’re often triggered by sun exposure and can come with other symptoms, such as joint pain.

Subacute Cutaneous Lupus Erythematosus

SCLE can occur anywhere on the body, but is usually in areas that are exposed to the sun, such as the neck, arms, shoulders, and legs.

The rash that occurs with SCLE may look very similar to plaque psoriasis. It might have areas of scaly, red, or darker skin with distinct edges, but it usually doesn’t have the silvery scale. An SCLE rash can also form in a ring-shaped pattern with darker borders and a lighter center.

Although SCLE may look like psoriasis, clues such as a ring-shaped pattern, a rash on sun-exposed skin, and flares after time in the sun can point toward lupus. The rash usually doesn’t leave a scar, but it may result in patches of lighter skin when it clears.

Chronic Cutaneous Lupus

There are several types of chronic cutaneous lupus. The most common is called discoid lupus due to the shape of the rash.

Discoid lupus usually appears as coin-shaped, thick, scaly patches of skin that are red or darker in color. Lesions commonly appear on the scalp and face but can be anywhere on the body.

Discoid lupus lesions can also look like psoriasis and may itch. However, they usually aren’t painful. Discoid lesions on the scalp may cause permanent hair loss. Without treatment, these patches can stay on the skin for years. People with a darker skin tone may notice that when discoid lupus clears, a discolored patch that is either darker or lighter than the surrounding skin is left behind.

Lupus and Psoriasis Treatment

Many of the treatment options for psoriasis and cutaneous lupus are similar. Topical medications applied to the skin can treat a rash caused by psoriasis or lupus. Creams, ointments, or lotions with anti-inflammatory medications, such as a corticosteroid, can improve symptoms of the rash.

Oral medications and biologics may also be used to decrease inflammation all over the body for both conditions. Keep in mind, though, biologics that work well for one condition may not be approved or work well for the other.

Although some medications can be used for either psoriasis or lupus, certain treatments may trigger the other condition.

For example, the antimalarial medication hydroxychloroquine, which is used to treat lupus, has been reported to start or worsen psoriasis in some people. This doesn’t happen to everyone, and the evidence is limited.

Another example is phototherapy, which can be used to treat psoriasis symptoms. But ultraviolet (UV) light can provoke or worsen photosensitive cutaneous lupus (lupus rashes in skin that is unusually sensitive to sunlight or other sources of UV light). For many people with cutaneous lupus, phototherapy may not be appropriate or may need extra caution.

Whether you’re living with psoriasis, lupus, or any other chronic condition that causes skin changes, keep an eye out for any unusual symptoms and talk to your doctor right away.

Remember, an accurate diagnosis is key to effective treatment, and your doctor can work with you to develop a plan to manage your condition and improve your quality of life.