The organs of your chest and abdomen are lined with thin layers of tissue called serous membranes. They have two layers: one connected to the organ and the other connected to the inside of your body cavity.
Between the two layers, there’s a thin film of serous fluid that allows your organs to move smoothly within your body. For example, your lungs can expand when you take a deep breath without being damaged by friction.
Serositis occurs when your serous membranes are inflamed. This makes it hard for your organs to smoothly slide around in your body, causing pain and other symptoms.
There are three types of serositis, depending on the serous membrane involved.
Your heart is surrounded by a serous membrane called the pericardium. Inflammation of this membrane is called pericarditis. It usually causes sharp chest pain that travels to your shoulder and changes as you change positions.
Depending on the cause, other symptoms may include:
- shortness of breath that gets worse when you lie down
- low-grade fever
- heart palpitations
- swelling in your legs or abdomen
Pleuritis, also called pleurisy, is inflammation of the pleura, the membrane that surrounds your lungs. There’s one serous membrane around each lung, so it’s possible to have pleuritis in one lung but not the other.
Pleuritis symptoms include:
- a sharp pain in your chest when you cough or breathe
- shortness of breath
- difficulty breathing
- low-grade fever
Your abdominal organs are surrounded by a serous membrane called the peritoneum. Inflammation of this membrane is called peritonitis. The main symptom of peritonitis is severe abdominal pain.
Other potential symptoms include:
- abdominal bloating
- nausea and vomiting
- low appetite
- diarrhea or constipation
- limited urine output
- extreme thirst
Systemic lupus erythematosus (SLE) is an autoimmune disease, which refers to any condition that involves your immune system mistakenly attacking your body instead of protecting it. It’s the most common type of lupus, and the condition that most people are referring to when they talk about lupus.
In the case of SLE, your immune system attacks healthy tissues in your body. Sometimes, this includes the tissue of your serous membranes, especially your pericardium and pleura. For example, a 2017 study of 2,390 people with SLE found that 22 percent had pericarditis and 43 percent had pleuritis. While less common, peritonitis can also be a cause of abdominal pain in people with SLE.
Serositis is one of the main things doctors look for when diagnosing someone with SLE.
Other immune system conditions
Your immune system has two parts, known as your acquired immune system and innate immune system.
Your acquired immune system develops as you’re exposed to viruses and bacteria over the years. It makes specific antibodies to each infectious agent you’re exposed. These antibodies are reactivated if you ever encounter the agent again.
Your innate immune system uses your white blood cells to attack viruses and bacteria. It reacts quickly to an infection, but it doesn’t produce cells that will remember if you’re exposed to the same infection in the future.
Autoimmune conditions involve your acquired immune system mistakenly attacking your body. Examples of autoimmune conditions that can cause serositis include:
Autoinflammatory conditions, on the other hand, involve your innate immune system mistakenly attacking your body.
Some autoinflammatory conditions that can involve serositis include:
- familial Mediterranean fever
- Still’s disease
In addition to autoimmune and autinflammatory conditions, several other conditions can cause serositis, either in one or all of your serous membranes.
Some examples include:
Your doctor may perform a physical exam and order blood tests and/or scans to help with a diagnosis. Blood tests help to look for signs of infection or markers of immune diseases. Scans such as a chest X-ray, CT scan, ultrasound, or electrocardiogram (ECG or EKG) may help to identify the source of the symptoms.
If there’s a lot of extra fluid between your serous membranes, your doctor can remove some of it with a needle and analyze it to help determine what might be causing it. This can be done easily for peritonitis and pleuritis.
For pericarditis, your doctor will usually use an ultrasound to help guide the needle and make sure it doesn’t puncture your heart.
Treating serositis depends on the underlying cause, as well as the serous membranes involved. To start, your doctor might suggest taking nonsteroidal anti-inflammatory medication, such as ibuprofen (Advil, Motrin), to reduce inflammation.
Once the underlying cause is determined, some possible treatment options include:
- immunosuppressant medications
- antiviral medications
Serositis refers to inflammation of one or more your serous membranes. Many things can cause it, from bacterial infections to autoimmune conditions. If you think you might have serositis, it’s important to follow up with your doctor to determine what’s causing it.