Dr X.

Deep vein thrombosis of the thigh — "silent killer"

This is a disease that has almost no symptoms. Only sometimes it is manifested by swelling of the lower extremities and pain in them.

There is a thrombosis of the deep veins of the thigh due to a slowdown in the outflow of blood from the lower extremities.
Blood clots themselves often form near venous valves☝🏻
These blood clots can "come off" and get into the pulmonary artery and cause its blockage.

Pulmonary embolism develops, which quite often leads to death.