Reddish-brown spot on the shin. What is it?

What is this spot? – The skin "rusting"

The discoloration is actually caused by “rust”, i.e. deposited oxidized iron in the skin. It forms when red blood cells leak out of the smallest vessels (capillaries) in larger numbers into the tissues. When these red blood cells break down, the iron released from their hemoglobin converts into hemosiderin. It is stored in the subcutaneous tissue and appears on the shin as a brownish-reddish spot.

The spot itself is not painful and does not itch – but from a medical perspective it is an important sign: it indicates persistent venous circulation disturbance and, in advanced cases, may be a precursor of venous leg ulcer.

How does hemosiderin deposition develop?

Your heart pumps blood through the arteries to the rest of your body; then it returns to your heart through the veins. Circulation is maintained by your heart, the diaphragm and respiratory muscles, and by contraction of your muscles during movement.

Veins contain "valves" — so-called venous valves — that permit blood to flow only one way (back toward the heart). As long as these valves close properly, they prevent blood from falling back toward the leg.

The problem arises when these valves weaken or the vein dilates. If this happens, the valve "lets go" and upward blood flow worsens. More and more blood remains in the veins; they swell, dilate and become tortuous (commonly called varicose veins).

If the condition persists, the increasingly distended vein wall becomes overstretched and begins to "leak" — red blood cells escape into the surrounding tissues. From the hemoglobin of the destroyed red blood cells iron is released, converted to hemosiderin, and deposited in the skin, creating the characteristic reddish-brown spot.

What lies behind the spot? – Venous hypertension and venous insufficiency

Reddish-brown discoloration of the lower leg is most often caused by venous problems, especially when pressure in the leg veins is persistently elevated. This condition is known as venous hypertension or venous insufficiency.

Your risk is higher if:

• your job requires long periods of standing or sitting without movement;
• your parents or siblings have similar leg problems (family tendency);
• you are being treated for varicose veins or leg ulcers;
• you have had deep vein thrombosis in the past — details in the thrombosis article, PTS section.

The classic, often years-unnoticed background is chronic venous insufficiency: if at the end of a long day your leg feels heavy ("as if you were wearing lead boots"), hurts or swells, that is not a good sign. The appearance of brownish-red spots and thin, dry skin around them indicates CEAP C4 stage — detailed classification in the chronic venous insufficiency article.

What can the spot indicate? – Differential diagnosis

The reddish-brown spot can point to three main backgrounds:

If leg edema is also present, the triage article helps with differential diagnosis: Leg swelling (edematous leg) causes and treatment.

What to do if reddish-brown spots appear?

If the spots have appeared, you are somewhat late for prevention — nevertheless, see a vascular surgeon clinic and request an evaluation. It is necessary to determine the severity of the problem; based on that, treatment can be set up to prevent further worsening.

At the clinic, in addition to history and physical examination, a Doppler ultrasound is usually performed. Its essence is to determine blood flow velocity in the leg vessels using ultrasound and to compare both sides.

Further tests may be needed to assess diabetes or cardiac involvement.

How can the spot and its cause be treated?

Hemosiderin deposited in the skin cannot be removed — the discoloration will therefore accompany you for life. What you can do is prevent or slow further deterioration and treat the underlying venous insufficiency.

Skin hydration

The skin of the discolored area thins, becomes dry and may crack. Avoid drying soaps. Use a moisturizing cleanser or cosmetic. Bath water should not be too hot — that also dries the skin. Do not use coarse towels or bath mitts, you may injure the thin skin.

Compression therapy

There are two types of compression options: elastic compression stockings made of stretchable material or machine pneumatic massage (intermittent pneumatic compression), often referred to as a lymphatic massage machine. Compression therapy supports venous blood flow, effectively reduces swelling, promotes healing and helps prevent wounds or ulcers.

Functional electrical stimulation (FES)

A significantly cheaper (though somewhat less effective) method than pneumatic compression is electrical stimulation of the lower limb muscles. The muscle contractions triggered by the impulses support limb circulation similarly to muscle movement. Favorable results can be expected after a few weeks of daily 20–30 minute sessions.

Exercise – the natural “pump”

The natural motor of venous circulation is regular muscle contraction, i.e. movement. To support venous circulation, brisk walking, jogging or cycling are most suitable. Move as often as possible: ideally 20–30 minutes once or twice a day, or a single 40–50 minute session. In this case, more is better!

Prevention – what you can do to avoid it

Since shin discoloration is a consequence of venous insufficiency, if you don't want reddish-brown spots on your legs, prevent them. The most effective method is daily regular exercise. Start in childhood and never stop exercising.

Scientific background