Raynaud phenomenon

Raynaud phenomenon is a phenomenon where there’s vasoconstriction of arteries near the skin that make a body part, often the fingers, turn white, then blue, and then red in response to a trigger like cold weather.

The phenomenon is named after Auguste Gabriel Maurice Raynaud, a French physician, who first described it.

To clear up some potentially confusing terminology, it’s called Raynaud disease or primary Raynaud phenomenon where the condition occurs alone and is not associated with any other disease, and it’s called Raynaud syndrome or secondary Raynaud phenomenon when it is associated with diseases like systemic lupus erythematosus or scleroderma.

Normally blood flows from large arteries into medium-sized or muscular arteries, and then into small arterioles which carry the blood to capillary beds.

All arterial vessels have three layers: from inside moving out, there’s the endothelium, then the media layer which contains smooth muscle, and finally the adventitia layer which has loose connective tissue and nerves.

Some nerve fibers in the skin function as thermoreceptors, which sense changes in temperature.

When stimulated, they cause the nerve to fire, sending signals up through the spinal cord to the hypothalamus, which is at the base of the brain.

The hypothalamus serves as the body’s thermostat because it coordinates the brain’s response to temperature changes.

The hypothalamus is what triggers the thought – “Hey, it’s pretty cold here. Maybe I should find a friendly llama to snuggle with for warmth.”

The hypothalamus also coordinates changes in the sympathetic and parasympathetic nervous system.

For example, normally, there’s a lot of heat energy in the blood, that gets lost to the environment.

When the sympathetic nervous system gets stimulated it causes contraction of smooth muscle that wraps around arterioles causing vasoconstriction and a reduction of blood flow to the skin.

That shunts blood away from the skin and towards the body’s core or organs where less heat energy is lost.

In Raynaud phenomenon, triggers like the cold or even emotional stress cause sympathetic nerves in the walls of arterioles to get overstimulated, and that makes the arterioles vasoconstrict.

If the vasoconstriction happens briefly or intermittently it’s called vasospasm.

When the arterioles vasoconstrict it dramatically decreases blood flow to downstream tissue.

For example, if there’s vasospasm in the arterioles in the fingers, it causes the fingers to turn white reflecting ischemia, then blue reflecting hypoxia, which is the low oxygen state that occurs after prolonged ischemia.

Finally, once the vasospasm ends, oxygenated blood rushes into the tissue, causing what’s called reactive hyperemia, which makes the fingers look red.

This rush of blood rush is thought to be the cause of swelling, tingling, and pain that some people experience at this point in the episode.

Now, there are a few important differences between primary and secondary Raynaud phenomenon.

Primary Raynaud phenomenon usually affects the fingers and toes symmetrically, and the severity stays roughly constant over time.

The arteries themselves typically remain undamaged unless the episodes occur frequently over many years, in which case there may be some thickening of the arterial wall.

The most common triggers are stress and cold temperatures, but other potential triggers include nicotine and caffeine, and as well as medications that affect the sympathetic nervous system like pseudoephedrine.

Primary Raynaud phenomenon is common among pregnant women and is common among those who work in jobs that require lots of vibration, like using a jackhammer.

In contrast, secondary Raynaud phenomenon usually affects fingers and toes asymmetrically, and there is often progressive severity because there’s often underlying damage to the arteries.

It is also often associated connective tissue disorders like systemic lupus erythematosus and scleroderma, as well as vasculitides like Buerger’s disease and Takayasu’s arteritis.

Symptoms of Raynauds disease include color changes in the fingers and toes, as well as numbness, tingling, and pain once blood returns.

Sometimes it can affect the nose, ears, and lips – all of those places that get cold in the snow.

If the vasospasm gets severe enough, this lack of blood flow can cause tissue death.

The diagnosis of Raynaud’s disease is usually based on description of the episodes, and exploring for a possible underlying condition.

Occasionally, nailfold capillary microscopy is done to see whether finger capillaries are normal appearing, which would be consistent with primary Raynaud phenomenon, or if they’re damaged which would be consistent with secondary Raynaud phenomenon.

Treatment includes avoiding triggers like cold temperatures, stress, smoking, and caffeine, and occasionally using a medication like a calcium channel blocker to help with vasodilation of the arteries.

In severe cases, surgery can be done to cut the sympathetic nerve fibers supplying the affected areas.

Summary

All right, as a quick recap… Raynaud phenomenon is vasospasm of arterial blood vessels that causes a body part, often the fingers, to change from white, to blue, and then to red once the vasoconstriction ends.

It’s most commonly triggered by cold exposure or emotional stress.

It’s called Raynaud disease or primary Raynaud phenomenon when it happens alone, and is called Raynaud syndrome or secondary Raynaud phenomenon when it happens along with another disease process.