[4] 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.
[6] Most SCLS patients succumb to viral infections manifesting themselves by way of flu-like symptoms (like a runny nose), gastro-intestinal disorders (diarrhea or vomiting), or general weakness or pain in the limbs, but others get no particular or consistent warning signs ahead of their episodes.
They subsequently develop thirst and lightheadedness and the following conditions measurable in a hospital emergency-room setting: [4][5][7] Although the precise molecular cause of SCLS remains undetermined, scientific research in recent years, conducted mainly at a unit (NIAID) of the U.S. National Institutes of Health, has shed some light on its biological and chemical roots.
The study of the peripheral microvasculature from patients’ biopsy specimens has not evidenced gross anomalies, disrupted angiogenesis, or inflammatory cells or other factors suggestive of a disorder prone to damage the blood vessels by inflammation.
The characteristic triad of profound arterial hypotension, hemoconcentration (elevated hematocrit, leukocytosis, and thrombocytosis), and hypoalbuminemia in the absence of secondary causes of shock and infection, requires diagnosis in a monitored hospital setting during or after an acute episode.
The fact that the condition is exceedingly rare – an estimated one per million inhabitants – and that several other diseases exhibit features akin to SCLS, including secondary capillary-leak syndrome or hypoproteinemia, militate against early identification.
[4][5] The most common clinical features are flu-like symptoms such as fatigue; runny nose; lightheadedness up to and including syncope (fainting); limb, abdominal or generalized pain; facial or other edema; dyspnea; and hypotension that results in circulatory shock and potentially in cardiopulmonary collapse and other organ distress or damage.
Urgent medical attention in this phase often features fluid resuscitation efforts, mainly the intravenous administration of saline solution plus hetastarch or albumin and colloids (to increase the remaining blood flow to vital organs like the kidneys), as well as glucocorticoids (steroids like methylprednisolone, to reduce or stop the capillary leak).
Consequently, fluid resuscitation should be minimized as much as possible in patients experiencing episodes of SCLS, and they should be closely monitored in a hospital intensive-care setting including for orthopedic complications requiring surgical decompression.
[5][13][14] The second, more recent approach pioneered in France during the early 2000s involves monthly intravenous infusions of immunoglobulins (IVIG), with an initial dose of 1-2 gr/kg/month of body weight, which has proven very successful as per abundant case-report evidence from around the world.