Capillary Leak Syndrome: What It Is, Causes, Symptoms, and Treatment

Capillary Leak Syndrome, known medically as Systemic Capillary Leak Syndrome (SCLS), was first described in 1960 by Dr. Bayard Clarkson, which is why it is also referred to as Clarkson’s disease. This syndrome can have a severe course due to the shock state that develops during its progression, making awareness of the condition crucial.

What Is Capillary Leak Syndrome?

Capillary Leak Syndrome is a rare disorder characterized by episodes in which a large portion of the blood’s plasma leaks out of blood vessels into surrounding tissues, such as spaces in the muscles or surrounding tissues. These episodes result in a sudden drop in blood pressure, leading to shock. If left untreated, this shock can progress to organ failure and eventually result in death.

This syndrome shares similar features with other serious conditions, such as septic shock from severe infections or anaphylactic shock from intense allergic reactions. Therefore, distinguishing Capillary Leak Syndrome from these similar conditions is very important. Sometimes, episodes of capillary leak syndrome may be triggered by an upper respiratory infection or physical exhaustion. The frequency of these episodes varies from person to person. In some individuals, only a single episode of capillary leak syndrome may occur, while in others, it can happen multiple times a year.

What Are the Symptoms of Capillary Leak Syndrome?

After studying individuals with this syndrome, Dr. Clarkson identified symptoms that include sudden onset of fever, a rapid drop in blood pressure, and a noticeable swelling (edema) that is particularly pronounced in the face, legs, and arms. Following these developments, many individuals also experience excessive urination within a few days, which can reduce the swelling in the arms and legs. In some cases, pulmonary edema (fluid accumulation in the lungs) can lead to heart failure, potentially causing life-threatening outcomes.

Symptoms associated with Capillary Leak Syndrome can resemble those of many other conditions:

• Restlessness
• Fatigue
• Abdominal pain
• Nausea
• Muscle pain
• Excessive thirst
• Sudden weight gain

In cases where an upper respiratory infection triggers the condition, symptoms like nasal congestion and cough may serve as warning signs of a syndrome episode.

As blood continues to leak from vessels into surrounding tissues, blood volume and pressure decrease. This can result in oxygen and nutrient deficiencies in organs such as the kidneys, brain, and liver. Lack of adequate blood flow to these organs may lead to multiple organ failure due to hypoperfusion (reduced blood supply), and blood thickening due to fluid loss can increase clotting tendencies, accompanied by widespread edema.

What Causes Capillary Leak Syndrome?

While the exact cause of Capillary Leak Syndrome is unknown, it may stem from an inflammatory process. Studies in Europe have noted that patients often experience flu-like symptoms shortly before an episode. Upper respiratory infections caused by agents such as influenza, RSV, or West Nile virus may act as primary triggers. Physical exhaustion from extreme heat or prolonged travel can also be potential triggers.

As the syndrome progresses, patients experience rapid shock and widespread swelling. During what is known as the “leak phase,” up to 70% of blood plasma volume escapes the blood vessels, and this phase may last for several days.

The severity and frequency of capillary leak episodes vary among individuals and over time. In severe cases, a drop in blood pressure of around 60 mmHg and loss of consciousness may necessitate intensive care. In milder cases, patients may experience moderate symptoms such as fatigue, dizziness, and excessive thirst.

How Is Capillary Leak Syndrome Diagnosed?

The primary diagnostic criteria for Capillary Leak Syndrome are referred to as the “3 Hs”: Hypotension (low blood pressure), Hemoconcentration (thickening of the blood), and Hypoalbuminemia (reduced levels of albumin in the blood). Diagnosis also requires ruling out other conditions that could cause these symptoms. Typical signs include bilateral edema in the face, trunk, arms, and legs after fluid restriction. Blood tests often reveal elevated hemoglobin levels due to blood thickening.

For suspected cases, initial diagnostics involve routine blood and urine tests to exclude other possible conditions. Subsequent immunological studies may indicate signs of the syndrome but are not specific to it. Therefore, diagnosis is based on the individual’s overall clinical presentation.

Further testing may help identify the underlying causes of symptoms like hypotension and edema. Tests such as lung imaging, electrocardiography (ECG), and echocardiography (ECHO) may be useful for evaluating possible heart failure and kidney function.

How Is Capillary Leak Syndrome Treated?

Systemic Capillary Leak Syndrome is a rare disease characterized by sudden, severe episodes. These episodes begin when blood leaks out of vessels, causing abrupt hypotension (low blood pressure). Immediate intervention is often required due to the potential for severe complications over several days.

Because the root cause of the syndrome remains unclear, there is no targeted treatment. The primary goal of treatment is to control symptoms and prevent severe complications during episodes.

Treatment for suspected cases takes place in an intensive care setting. Patients receive intravenous fluids to maintain blood volume, reducing the risk of organ failure. Patients who receive large fluid volumes are closely monitored.

In some cases, monthly intravenous immunoglobulin (IVIG) therapy can prevent future episodes. Some asthma medications may also be beneficial as a preventive measure, though they may cause side effects such as hand tremors.

Generally, treatment for capillary leak syndrome is supportive. While regular IVIG therapy shows promise for some patients, it is costly. Because there is currently no targeted treatment, individuals who observe symptoms of this condition should seek immediate medical support from specialists at a nearby healthcare facility.