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Systemic capillary leak syndrome.

Systemic capillary leak syndrome (SCLS) is characterized by recurrent crises of hypovolemic hypotension, hemoconcentration, hypoalbuminemiawithout albuminuria, generalized edema, and in most cases, the presence of a paraprotein (without any evidence of multiple myeloma) (1 , 2). The clinical signs result from massive extravasation of plasma and its constituents from the intravascular into the extravascular space as a result of a sudden reversible increase in capillary permeability. At the initial phase of an attack, the pulmonary vasculature is spared and pulmonary edema does not occur. Crisis is heralded with abdominal pain, nausea, and dizziness and its end is characterized by rapid polyuria. Infections, especially viral infections are suggested to trigger SCLS(2). Death during the acute attack can occur from cardiopulmonary collapse. Capillary permeability is normal during quiescent periods. The pathogenesis of SCLSis unknown. Clarkson et al (1) in 1960 induced hypotension in rats by injecting a plasma sample obtained from patients with active SCLS, suggesting the presence of a circulating factor that alters vascular permeability. This could not be reproduced in other studies using serum, plasma, or purified paraprotein (3). Subsequent studies have suggested a possible role for leukotrienes, cytokines, and complement in the pathogenesis of SCLS(2). During crises of SCLS, increased production of leukotriene B4, increased interleukin-2-receptor-positive mononuclear cells surrounding the blood vessels, and an increase in serum levels of a soluble interleuin-2 receptor have been detected. Moreover, generalized edema due to extravasation of intravascular fluid, closely resembling SCLS, has been observed in patients receiving high dose recombinant interleukin-2 (4). Thus, cytokines secreted by the plasma cell clone could explain the capillary hyperpermeability. Recently Assaly et al (5) proposed endothelial apoptosis as a potential mechanism for capillary hyperpermeability. They demonstrated that components from the sera of patients with active SCLSmediate oxidation-induced endothelial apoptosis in vitro. The previous electron microscopic study in muscle tissue of SCLS patients (6) did not show widening of interendothelial gaps but revealed increased endothelial microvesicular bodies and pedunculated blebs. The findings are now recognized as signs of apoptosis. Assaly et al (5) suggested that anticaspases and/or antioxidant may have a therapeutic value in the treatment of SCLSby inhibiting the endothelial apoptosis. Numerous regimens based on possible mechanisms have been tried for prophylaxis with varying success (2). A recent report (7) has suggested the regimen of terbutaline and theophylline to be an effective prophylaxis against SCLS. Both terbutaline ((32-stimulants) and theophylline (phosphodiesterase inhibitor) increase intracellular cyclic AMPand mayimprove capillary hyperpemeability through endothelial cell relaxation. In addition theophyllin has anti-inflammatory properties which modulate cytokine production. To limit the risk of precipitating factors leading to attacks, dental and sinus infections are recommendedto be cured. During the capillary leak phase, judicious fluid support to maintain perfusion of the vital organs is crucial. Central venous monitoring and placement in an intensive care unit are necessary. For the early institution of management,patients should be instructed to return to the hospital at the onset of the prodrome. Profound hypoalbuminemia limits the efficacy of available plasma expanders. Attempts at normalizing blood pressure frequently worsen edema and predispose the patient to pulmonary edema during the recruitment phase. The patient reported by Chihara et al (8) in this issue of the Journal recovered from hypovolemic shock but developed acute pulmonary edema. The report indicates the importance of timely switch from managementof severe hypovolemia to that of acute fluid overload whenthe recruitment phase starts. Corticosteroids may have a role whencytokine-mediated endothelial damageinitiates the capillary leak. Loop diuretics are effective to manage fluid overload during the recruitment phase. If kidney function is compromised, hemodialysis or hemofiltration should be done.