Capillary leak syndrome

Capillary leak syndrome, or vascular leak syndrome, is characterized by the escape of blood plasma through capillary walls, from the blood circulatory system to surrounding tissues, muscle compartments, organs or body cavities. It is a phenomenon most commonly witnessed in sepsis, and less frequently in autoimmune diseases, differentiation syndrome, engraftment syndrome, hemophagocytic lymphohistiocytosis, the ovarian hyperstimulation syndrome, viral hemorrhagic fevers, and snakebite and ricin poisoning.^[1] Pharmaceuticals, including the chemotherapy medications gemcitabine and denileukin diftitox, as well as certain interleukins and monoclonal antibodies, can also cause capillary leaks.^[1][2] These conditions and factors are sources of secondary capillary leak syndrome.

Systemic capillary leak syndrome (SCLS), also called Clarkson's disease, or primary capillary leak syndrome, is a rare, grave and episodic medical condition observed largely in otherwise healthy individuals mostly in middle age.^[3] It is characterized by self-reversing episodes during which the endothelial cells which line the capillaries, usually of the extremities, separate for one to three days, causing a leakage of plasma mainly into the muscle compartments of the arms and legs. The abdomen, the central nervous system, and the organs (including the lungs) are typically spared, but the extravasation in the extremities is sufficiently massive to cause circulatory shock and compartment syndromes, with a dangerous hypotension (low blood pressure), hemoconcentration (thickening of the blood) and hypoalbuminemia (drop in albumin, a major protein) in the absence of other causes for such abnormalities.^[3][4] SCLS is thus a limb- and life-threatening illness, because each episode has the potential to cause damage to limb muscles and nerves, as well as to vital organs due to limited perfusion.^[3][4] It is often misdiagnosed as polycythemia, polycythemia vera, hyperviscosity syndrome, or sepsis.^[3]