Deep venous insufficiency of the lower extremities This is the most common cause. Patients present with visually visible varicose veins in the lower extremities, darkening of the skin (hyperpigmentation) and ulcers in the lower middle third of the lower leg. Traffic venous reflux is an important factor in ulcer formation. Lower extremity deep vein thrombosis sequelae This is the second most common cause and is easily overlooked or misdiagnosed. Patients present similarly to venous valve insufficiency, with visually visible varicose veins in the lower extremities, darkened skin (hyperpigmentation) and ulcers in the mid and lower third of the lower leg.