Muscle biopsy findings in systemic capillary leak syndrome.

Two patients with systemic capillary leak syndrome (SCLS) were followed up clinically for 5 and 2 years, respectively. Muscle biopsy was performed 1 week after the end of an acute crisis in one patient, and after 3 years in the other. In both cases, muscle capillary basement membranes were extremely thick--more than 15 times thicker than normal. Capillary basement membrane enlargement appears to be a permanent lesion, probably limited to muscle vessels. This finding has not been previously reported in SCLS, and would appear to indicate a relationship with the pathogenesis and severity of the crisis.