 Pharmaceuticals, including the chemotherapy medications gemcitabine and tagraxofusp, as well as certain interleukins and monoclonal antibodies, can also cause capillary leaks.These conditions and factors are sources of secondary capillary leak syndrome.Systemic capillary leak syndrome (SCLS, or 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.