Erythromelalgia

The condition is rare but recognisable: the feet, and less often the hands, suddenly start to burn from the inside, the skin over them turns red and feels hot to the touch. A flare is switched on by warmth — a duvet, tight shoes, a hot shower, a long walk — and switched off by cool. Hence the main trap of this condition: relief from cold comes so reliably that people spend years plunging their feet into iced water and end up taking more harm from the cold than from the illness itself. And there is a second reason not to put the investigation off: in some people erythromelalgia is not a disease in its own right but the first signal of a change in the blood, and that signal can run years ahead of everything else.

What a flare feels like

Three things come together: burning, redness and heat. The pain is described not as aching but as a scald; it often starts with itching or tingling that turns into burning within minutes. On brown and black skin the redness shows up less well, so there you go by the heat and the swelling rather than the colour. The area really is hot: the difference is easy to feel by laying a palm on each foot at the same time.

What else happens:

• swelling of the feet or hands and heavier sweating in exactly those areas;
• a flare builds up over an hour or two on some occasions and within minutes on others, and lasts anything from a few minutes to several days;
• usually both feet are equally affected, though one-sided involvement does occur;
• besides the feet and hands, the skin of the ears, nose and cheeks may burn, and less often the forearms and lower legs;
• as the flare lets go, the skin often turns the other way: cold and bluish;
• nights are worse than days: under the duvet the feet warm up and the burning wakes the person.

Between flares the skin looks entirely ordinary, and on a quiet day there is essentially nothing for a doctor to look at. That is why photographs taken in daylight at the height of a flare are worth more than any description.

What switches a flare on

The trigger is almost always the same one: warming. Not body temperature as such, but warming of the limb itself and everything that leads to it:

• hot weather, an overheated room, a hot bath, a hot water bottle, a heater under the desk;
• warm, tight clothing, thick socks, closed shoes, particularly rubber and synthetic ones;
• exercise, long walking and standing, and simply letting the legs hang down;
• alcohol and spicy food;
• not drinking enough;
• stress and short sleep — they do not set off a flare on their own, but they lower the threshold noticeably.

It is worth keeping brief notes for a fortnight: what came before the flare, how long it lasted, what helped. Such a diary usually brings out two or three personal triggers the person had no idea about, and gives the doctor material that no test can provide.

Where it comes from

The distinction here matters, because both the investigation and the treatment follow from it.

Primary erythromelalgia stands on its own, with no other illness behind it. Some of these cases are inherited: they begin in childhood or adolescence, run through a family across generations, and are linked to a change in the gene for a sodium channel in nerve fibres. Put simply, the pain nerves of the foot fire where in other people nothing at all would happen. Many cases remain unexplained even after a full work-up, which does not mean the work-up was wasted.

Secondary erythromelalgia follows on from another disease, and that is the one not to be missed. The first thing looked for is bone marrow disease in which the blood carries too many cells: polycythaemia vera and essential thrombocythaemia. Burning in the feet can appear years before the changes become visible in a blood count, so one normal result taken once does not close the question for good. And the risk of clots those diseases bring can be prevented, and prevented well.

What else is checked:

• damage to the small nerve fibres, including in diabetes;
• autoimmune connective tissue disease;
• thyroid disorders;
• multiple sclerosis and other diseases of the nervous system;
• medicines, above all the vasodilators of the calcium channel blocker group, and certain drugs acting on the immune system and on hormones;
• poisoning by mercury and by some toxic mushrooms: rare, but described, and reversible if the cause is found.

What must not wait

Burning feet on their own are not a reason to call an ambulance. But this condition has complications and companions where waiting is expensive. Seek urgent help if any of the following appears:

• a toe or part of the foot turns dark, purple or black, goes cold and loses sensation — that is what disturbed flow in the small vessels looks like, and it has to be dealt with the same day;
• a sore or ulcer where you have been cooling the skin, particularly if it does not heal, if redness is spreading around it, if there is discharge or if a temperature has come up;
• sudden weakness of an arm or a leg, a drooping face, muddled speech, loss of vision in one eye;
• pain and swelling in one calf that feels hot and firm;
• sudden breathlessness or chest pain.

The last three are signs of a clot. They are not here for completeness: in some people there is a blood disorder behind the erythromelalgia that raises that risk. An ambulance is called in whatever way is usual in your country; in Spain, Italy, Portugal, Poland and Ukraine the single European number 112 works.

How the cause is tracked down

The diagnosis rests on the description: burning, redness and heat that come on with warmth and go with cool. Examination in a quiet spell usually shows nothing, and that is normal. Sometimes the doctor will ask you to keep the feet warm or to walk about in order to see a flare in person.

Far more important than the examination is the search for secondary causes. That normally starts with a full blood count, which because of the bone marrow diseases is repeated more than once, and where those are suspected, a test for the characteristic mutation in blood cells. Blood sugar and the thyroid are checked, and if needed the markers of autoimmune inflammation. If there is numbness or loss of sensation, damage to the small nerve fibres is looked for: a nerve conduction study is done, or a small piece of skin is taken. Genetic testing is considered when the illness began in childhood or when relatives have had something similar.

The doctor will go through your whole list of medicines without fail. If there is a possible culprit on it, it gets changed — but the doctor changes it, not you: some of those drugs were prescribed for something more dangerous than burning feet.

What is used to treat it

There is no single remedy here that suits everybody, and it is fairer to say so up front: the choice is made by trial. On the other hand, there are plenty of options.

• Treating the underlying disease. When a secondary cause is found, that is where treatment starts, and often that is enough on its own.
• Low-dose acetylsalicylic acid in erythromelalgia linked to the bone marrow diseases. The effect can be striking: the burning goes within a day and stays away for several. That response is itself a clue pointing to that cause. In the other forms of the illness the drug usually does not help, and it should not be taken without being prescribed.
• Topical treatments: gels, creams and patches with a local anaesthetic, and preparations based on the chilli substance. They do not work for everyone, but they carry almost no risk.
• Drugs that calm overexcited nerve fibres: the anticonvulsants used for neuropathic pain, some antidepressants at those same doses, and, in the inherited form, medicines acting on sodium channels. The names matter less here than patience: each one needs two or three weeks to show what it can do.
• Ordinary painkillers help little, and opioids are best not prescribed: the pain is chronic and the price of dependence outweighs the benefit.
• In severe cases infusions of medication into a vein and nerve blocks are discussed; these are done in hospital and are kept in reserve.

A word about the mind: chronic pain that stops you sleeping, putting shoes on and leaving the house in hot weather wears a person down. That is not weakness of character. Psychological support, above all the techniques for managing chronic pain, genuinely reduces how bad the pain is, and it is worth asking for it before you have run out of strength.

What you can do yourself

Start with what must not be done, because this point outweighs all the rest put together.

Do not put your feet in cold water and do not apply ice. Relief will come, and it is deceptive. Skin that is soaked regularly in cold water softens, cracks and stops healing; infection follows on top of that. That, and not erythromelalgia itself, is how people end up with ulcers that will not close and with surgery. If cooling is needed, cool with air: a fan, a cool floor, a cool — not frozen — gel pack through a cloth and only briefly.

What helps without doing harm:

• raising the feet on a chair, a cushion or the arm of the sofa; the higher they are, the sooner it eases;
• loose shoes and clothing, thin socks in natural fabric, open footwear indoors;
• drinking enough, especially in hot weather and after exercise;
• exercising at the cool times of day and in a cool place, choosing an effort that does not overheat you: swimming suits many people;
• in the evening, not overheating the bedroom and keeping the feet on top of the duvet — a separate light blanket for the feet solves it better than an open window in winter;
• cutting down on alcohol and spicy food if you have noticed a connection;
• checking the feet every day, as is done in diabetes: a crack or a rub on skin that has lost sensation is easy to miss until it turns into an ulcer.

Online consultation

Erythromelalgia is recognised from the account, and an account travels perfectly well through a screen. The doctor will work out whether what is happening fits erythromelalgia or another condition with similar complaints, look at photographs taken at the height of a flare, go through your trigger diary with you, arrange the tests that look for secondary causes and explain why some of them will have to be repeated. This is also the place to review your list of medicines, discuss where treatment should start and how long to wait for it to work, put together a plan for hot weather and for the night, and decide in good time when a referral to haematology or neurology is due and when watching is enough. The signs in the urgent section are not sorted out at a consultation: with those you are seen in person, the same day.

This material is for information only and does not replace medical advice.