Capillary Leak Syndrome

Capillary leak syndrome happens when fluid leaks from your small blood vessels into surrounding tissues. It requires immediate treatment to prevent a drop in blood pressure and other serious complications. Capillary leak syndrome can’t be cured, but you can reduce episodes by taking medications as prescribed.


What is capillary leak syndrome?

Capillary leak syndrome happens when plasma (the liquid part of your blood) leaks out of tiny blood vessels (capillaries). The fluid leaks into muscles, tissues, organs and body cavities (spaces that hold organs).

Capillary leak syndrome attacks, or episodes, can occur several times a year or only once. If capillary leak syndrome isn’t treated promptly, your blood pressure drops rapidly, leading to organ failure and even death.

Though there’s no cure for capillary leak syndrome, it’s important to get prompt medical treatment to manage symptoms. You may be able to prevent future episodes of systemic capillary leak syndrome with regular use of medications or infusions.

What are the types of capillary leak syndrome?

There are two major types of capillary leak syndrome:

  • Systemic capillary leak syndrome, also called primary capillary leak syndrome, or Clarkson’s disease, involves repeated episodes, usually in otherwise healthy people.
  • Secondary capillary leak syndrome is a single episode triggered by another disease, condition or medication.

Who might get capillary leak syndrome?

Systemic capillary leak syndrome is a rare disorder that affects less than 500 people worldwide. Systemic capillary leak syndrome mainly happens in middle age and is very rare in children. That said, the incidence might be higher, as people with systemic capillary leak syndrome may often be misdiagnosed.

Secondary capillary leak syndrome can happen in people of any age. Certain infections, diseases and medications may lead to capillary leak syndrome.

How does a capillary leak syndrome episode affect my body?

There are three stages to a capillary leak syndrome episode:

  1. Prodromal phase: This phase occurs one to two days before the attack. You may start experiencing symptoms, such as fatigue, thirst and sudden weight gain.
  2. Leak or resuscitation phase: This phase occurs during the attack. Fluids and albumin (protein found in blood plasma) leak from your capillaries into your tissue spaces. The flow of blood that carries oxygen to your tissues slows. Your blood pressure falls, and your red blood cells build up. The leakage results in hypovolemia, when the volume of blood in your body decreases.
  3. Post-leak phase or recruitment phase: This phase occurs after the attack. Your capillaries reabsorb fluids and albumin from your tissues, causing a fluid overload. As a result, your body could develop too much urine (polyuria) and fluid in your lungs (pulmonary edema).


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Symptoms and Causes

What causes systemic capillary leak syndrome?

The cause of systemic capillary leak syndrome is unknown. Researchers suspect that an immune system response to an illness or infection may cause the condition.

What causes secondary capillary leak syndrome?

Sepsis (a life-threatening complication of infection) most commonly causes secondary capillary leak syndrome. Other conditions that cause capillary leak syndrome include:

Certain medications, including the chemotherapy drugs gemcitabine (Gemzar®) and tagraxofusp (Elzonris®), may also cause secondary capillary leak syndrome.


What symptoms occur before a capillary leak syndrome episode?

Symptoms usually begin one or two days before a capillary leak syndrome attack. This is called the prodromal phase. These symptoms may include:

What symptoms occur during a capillary leak syndrome episode?

During a capillary leak syndrome episode (called the leak or resuscitation phase), symptoms may vary from person to person. Common symptoms can include:


Diagnosis and Tests

How do healthcare providers diagnose capillary leak syndrome?

Healthcare providers diagnose capillary leak syndrome by asking about your health history and doing a physical examination. They’ll check your blood pressure to see if it’s low.

Healthcare providers may also need to exclude other conditions before they can diagnose capillary leak syndrome. They may order blood tests to look for:

  • Increased levels of hematocrit (the number of red blood cells in your blood).
  • Increased levels of hemoglobin (a protein in your red blood cells).
  • Low protein in your blood (hypoalbuminemia).

They may also do a blood test to look for abnormal immunoglobin protein (monoclonal gammopathy, or M protein). People with capillary leak syndrome may have abnormal M protein in their blood.

Management and Treatment

How do healthcare providers treat capillary leak syndrome?

There isn’t a cure for capillary leak syndrome. Healthcare providers focus on managing symptoms and preventing complications.

During a capillary leak syndrome episode, healthcare providers try to control blood pressure to maintain blood flow to your organs. They also try to prevent excess swelling and fluid buildup. They may use:

  • Glucocorticoids: Steroids to reduce capillary leaks.
  • Intravenous fluids: Liquids to increase blood flow to organs such as your kidneys.

You’ll usually be hospitalized during an episode. During treatment, your healthcare provider will constantly monitor your vein and arterial pressure to ensure that too much fluid doesn’t build up in your body. Excess fluid can lead to other complications, including pulmonary edema (excess fluid in your lungs) and sudden cardiac arrest.

After the capillary leak syndrome attack (post-leak phase or recruitment phase), your healthcare provider may use a diuretic to decrease the fluid. A diuretic is a pill that helps your body get rid of water and salt through increased urine.


Can I prevent systemic capillary leak syndrome?

You can’t prevent systemic capillary leak syndrome from developing. Once you’ve had an attack, you know you have the condition.

Regular use of medications or infusions may help prevent future episodes and reduce their severity. These treatments may include:

  • Monthly infusions of intravenous immune globulin (IVIG).
  • Oral asthma medications, such as theophylline (Elixophyllin®), terbutaline (Brethine®) and montelukast (Singulair®).
  • Steroids to reduce inflammation.

Outlook / Prognosis

What is the outlook for people with systemic capillary leak syndrome?

Systemic capillary leak syndrome can usually be managed with preventive treatments. Treatments generally work better when people are diagnosed earlier and have fewer complications. Serious complications due to capillary leak syndrome may include:

Living With

When should I see my healthcare provider about capillary leak syndrome?

See your healthcare provider immediately if you think you’re experiencing the start of a capillary leak syndrome episode. They can help manage your symptoms and keep you more comfortable.

A note from Cleveland Clinic

Capillary leak syndrome is a condition where plasma leaks from your capillaries into other tissues of your body. Capillary leak syndrome can happen once or many times. Complications of untreated capillary leak syndrome can be serious. The sooner you’re diagnosed with capillary leak syndrome and begin treatment, the better your chances of a positive outcome.

Medically Reviewed

Last reviewed on 04/07/2022.

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