Rashes and swelling are two broad symptoms that can appear in many chronic conditions, including lupus and hereditary angioedema (HAE). Although these conditions are very different, people with HAE may have a higher risk of developing lupus and other autoimmune diseases.

If you have both HAE and lupus, you’re not alone. Research shows that around 2 percent of people with HAE also have systemic lupus erythematosus (SLE), the most common type of lupus.

Let’s take a closer look at the links between these two conditions and how doctors tell them apart.

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What Is Lupus?

Lupus is an autoimmune condition, which means the immune system mistakenly attacks healthy tissues. It causes inflammation throughout the body, including the joints, skin, heart, and kidneys. Untreated lupus can damage organs and tissues, resulting in complications like seizures, eye problems, kidney disease, and heart disease.

SLE causes symptoms throughout the body. Other types include cutaneous lupus erythematosus (lupus of the skin) and drug-induced lupus (temporary lupus symptoms resulting from medication).

Lupus Symptoms

Lupus can cause a wide range of symptoms.

Swelling (usually in the limbs or face), a butterfly-shaped rash across the nose and cheeks, and joint and muscle pain are among the most common lupus symptoms. Lupus can also cause:

• Headaches
• Fever
• Sores in the mouth
• Blood clots
• Fatigue

How Common Is Lupus?

Lupus is more common than HAE, affecting around 1.5 million people in the United States and around 5 million worldwide. For comparison, HAE is considered a rare disease and affects roughly 6,000 people in the United States.

Although HAE isn’t an autoimmune disease, it commonly occurs alongside autoimmune diseases like lupus. One in three people with lupus has multiple autoimmune conditions at the same time.

The Connection Between HAE and Lupus

Researchers are still studying the connections between HAE and lupus. Possible links may help explain why people with HAE could be more likely to develop lupus and other autoimmune diseases.

Connections in the Complement System

The complement system is a part of the immune system that first activates your body’s immune defenses when your body senses that something isn’t right. Its responsibilities include targeting potentially harmful invaders like viruses or bacteria and activating inflammation to prevent infections.

HAE stems from an issue within the complement system. Many people with HAE either don’t have enough of a protein called a C1 inhibitor (C1INH), or their C1INH doesn’t work as it should.

C1INH plays a key role in regulating the complement system. When you don’t have enough of it, or if it doesn’t work properly, it can lead to uncontrolled swelling.

Problems with the complement system are also linked to SLE. These include complement system deficiencies (like in HAE) and complement system activation. C1 inhibitor deficiencies, in particular, have been found to increase the risk of SLE.

Among autoimmune diseases, SLE is the most likely to be linked to problems with the complement system. It’s also the most common autoimmune disease in people with HAE.

Overlapping Symptoms Between HAE and Lupus

HAE and lupus share some of the same symptoms. Swelling is perhaps the easiest to recognize. Both conditions can cause symptoms that may be unpredictable.

In both lupus and HAE, symptoms tend to appear periodically. For people with lupus, the symptoms appear or worsen during flare-ups. People with HAE experience episodes of swelling called HAE attacks.

Both lupus flare-ups and HAE attacks can happen in response to triggers, but sometimes the triggers are unclear.

Swelling in Lupus vs. HAE

Lupus tends to cause swelling in areas like the legs, arms, and face during flare-ups. HAE attacks involve swelling that appears suddenly and can last for several days.

Like lupus swelling, HAE swelling often affects the face and extremities (arms and legs). Swelling can appear in other parts of the body in both conditions, too. For example, people with lupus often experience swollen glands.

HAE may cause swelling around the throat and airway, which can be a life-threatening emergency if it prevents breathing. Their intestines may also swell, which can cause severe abdominal pain.

Rashes in Lupus vs. HAE

Skin rashes are also associated with both HAE and lupus. In people with SLE, rashes can show up across the body. A butterfly rash across the nose and cheeks is an especially common type of rash in people with lupus.

Cutaneous lupus can cause a variety of skin symptoms, including butterfly rashes, scaly rashes, itching, and skin discoloration.

Rashes in HAE aren’t usually itchy, but they can appear during HAE attacks. A rash often appears shortly before an HAE attack as a warning sign.

Differences in Diagnostics

Diagnosing HAE usually looks quite different than diagnosing lupus. HAE can be diagnosed with blood tests for a C1INH deficiency. There is no single test for diagnosing lupus.

HAE is usually first diagnosed during childhood or adolescence. In some cases, symptoms can appear as early as 2 years old. When a child has HAE symptoms, doctors start with a physical exam before using blood tests to check their C1INH levels and function. In some cases, healthcare providers use genetic testing to check for gene mutations linked to hereditary angioedema.

Lupus is most often first diagnosed in adult women, though men and teenagers can get lupus, too. To diagnose lupus, doctors review the symptoms and perform a physical exam. After that, they may use blood tests, urine tests, biopsies, or other tests to diagnose lupus.

Treating Lupus vs. HAE

In both HAE and lupus, it can be helpful to keep track of potential triggers that may cause symptoms to appear. Stress and other triggers can lead to swelling in someone with HAE or cause a flare-up in someone with lupus.

Although not all HAE attacks and lupus flares have triggers, identifying and avoiding triggers can be an important step in the treatment for both conditions.

Lupus treatment aims to reduce the frequency of flare-ups, lessen symptom severity during flare-ups, and minimize organ damage. You may need a combination of medications to accomplish these goals.

HAE treatment can be split into two categories: on-demand treatments to treat ongoing HAE attacks and preventive treatments to reduce the frequency of attacks.

People with HAE may be prescribed a combination of medications to prevent and treat swelling. They may also require emergency care if swelling affects the airway.

As you may have noticed, treatment goals for HAE are similar to treatment goals for lupus. Preventing symptoms and treating them as they occur can help people with lupus, HAE, or both conditions reduce the risk of serious complications.

Talk to Your Doctor

If you have HAE and experience symptoms that don’t seem related to your HAE, talk to your doctor. A recurrent facial rash, fatigue, or muscle pain can be signs of lupus or other conditions that need treatment alongside your HAE. Your doctor can help you safely manage both conditions at the same time.

Join the Conversation

On myHAEteam, people share their experiences with hereditary angioedema, get advice, and find support from others who understand.

How do you manage HAE and lupus at the same time? Let others know in the comments below.