Blood clots. A blood vessel might be blocked by an embolus. It is a very small mass of particles that moves through the bloodstream. Or it could be blocked by a thrombus. This is the blood clot. Major lymphedema (rare): Some people are born without the need of specified lymph vessels https://www.sgvascularctr.com/a-comprehensive-approach-to-lymphoedema-treatment-a-vascular-surgeons-perspective/