CLINICAL PRACTICE: Clinical review Burning feet syndrome A clinical review

Ravinder P S Makkar, MD, is Medical Advisor, Department of Medical Assistance, International SOS, New Delhi, India. Anju Arora, MD, is attending physician, Department of Medicine, Sitaram Bhartia Institute of Science and Research, New Delhi, India. Amitabh Monga, MD, is attending physician, Department of Medicine, Sitaram Bhartia Institute of Science and Research, New Delhi, India. Ajay Kr Gupta, MD, is attending physician, Department of Medicine, Sitaram Bhartia Institute of Science and Research, New Delhi, India. Surabhi Mukhopadhyay, MD, is attending physician Department of Medicine, Sitaram Bhartia Institute of Science and Research, New Delhi, India.

BACKGROUND Burning pain in the feet has been known to occur as a distinct clinical symptom for almost two centuries. Despite being a common and fascinating clinical entity, this syndrome has received scant attention in the medical literature and has been described only in anecdotal reports. OBJECTIVE This article describes and discusses the various aspects of this intriguing syndrome. DISCUSSION Burning feet syndrome (BFS) is a common disorder especially among the elderly and is frequently encountered in general practice. There is no specific aetiology and it can occur as an isolated symptom or as part of a symptom complex in a variety of clinical settings. In contrast to the presence of distressing subjective symptoms, the physical examination is marked by a paucity of objective signs. The pathophysiology of BFS is not very clear and treatment varies depending on the aetiology.

urning feet syndrome (BFS), which is be divided into the following categories ciency related neuropathy before frank Bcharacterised by a sensation of (Table 1). neurological signs appear.8 No other vita- burning and heaviness in the feet and mins apart from the B-group have been lower extremities, is a common disorder Nutritional causes implicated in the cause of BFS. frequently encountered by general practi- Since its initial descriptions,1–3 BFS has Other conditions associated with tioners. In the past, this syndrome has been postulated to be caused by vitamin vitamin deficiencies such as chronic alco- been described only in anecdotal reports deficiency. The specific vitamin, however, holism, or patients on chronic and has received scant attention in the remains obscure, the deficient factor hemodialysis, can develop BFS possibly medical literature. Grierson1 was, in 1826, being variously attributed as riboflavin2,3 due to associated nutritional deficiencies.8 the earliest to document such a symptom, nicotinic acid,4 thiamine,5 and pyridoxine.6 but a detailed description was given by Most patients with burning feet show evi- Metabolic or endocrinal causes Gopalan2 in 1946, hence, BFS is also dence of riboflavin deficiency.7 Burning feet is commonly seen with dia- known as Grierson-Gopalan syndrome. It is suggested that vitamin B defi- betes. Patients with signs and symptoms ciency leads to disturbance in cellular of burning feet may be part of What causes ‘burning feet’? metabolism in the tissues causing accumu- related small fiber or autonomic neu- There is no specific aetiology for BFS. lation of intermediate metabolites which ropathies.9 The development of this It can occur as an isolated symptom or as may cause abnormal and excessive stimu- symptom in diabetics is related to some part of a symptom complex in association lation, or lower the pain and temperature extent to the severity and duration of the with a variety of unrelated clinical set- threshold of peripheral sensory nerve disease. Functional or organic abnormali- tings. Based on the underlying endings.2 It is also thought that BFS is an ties may be present in small mechanism, the various causes of BFS can early clinical phase of vitamin B12 defi- unmyelinated-C fibers.13 The dysfunc-

1006 • Reprinted from Australian Family Physician Vol. 31, No. 12, December 2002 Burning feet syndrome — a clinical review n tional phase can precede organic struc- characterised by burning pain and redness Table 1. Causes of BFS tural damage and symptoms may develop of the extremities and may be primary or without signs of overt neuropathy. secondary to systemic disorders such as Nutritional Burning feet can also occur in other diabetes, collagen vascular disorders, or • Vitamin B deficiency endocrine disorders such as hypothy- myeloproliferative disorders such as poly- • Malabsorption syndrome roidism, though the mechanism is not cythemia vera or essential thrombo- • Chronic alcoholism completely understood. cytosis.16 The symptoms of this disorder Metabolic/endocrinal are probably related to intravascular • Diabetes mellitus Hereditary platelet aggregation and may involve a • Renal failure (dialysis patients) • Familial disorder with an autosomal hyperactive axon reflex in C-nociceptive dominant inheritance may cause BFS.11 fibers or a mutation of the capsaicin Hereditary • Autosomal dominant BFS The clinical picture is that of bilateral receptors.17 symmetrical pain with no muscle weak- Other unrelated and less common Mechanical (entrapment neuropathies) ness, atrophy or foot deformity. Initially, conditions with symptoms of burning feet • • Traumatic nerve compression it was thought that BFS may be the sole are chronic mountain sickness,18 leishma- manifestation of an hereditary sensory niasis,19 Gitelman syndrome20 (a rare renal Psychosomatic neuropathy (HSN), but subsequently, tubular disorder), and carnitine deficiency Miscellaneous molecular genetic studies excluded state.21 Patients who do not reveal any • linkage to HSN locus on chromosome abnormalities even after exhaustive labo- • Chronic mountain sickness 12 • Gitelman syndrome 9q22 and 3q13–q22. Therefore, it is ratory investigations are usually labelled • Leishmaniasis concluded that autosomal dominant idiopathic. • Multiple sclerosis burning feet represents a distinct clinical Idiopathic entity in itself. Clinical features Although no geographical or seasonal Mechanical causes variation is known, BFS has been mainly Burning feet syndrome may occur as a reported in Asian and Far East countries result of mechanical compression of the during a hot summer.3–5 It is most peripheral nerves (as seen in tarsal tunnel common in those over 50 years, although warm overlying skin as in erythromelal- syndrome) and in diseases such as it can occur in any age group. Usually dis- gia.16 There is no local tenderness over the hypothyroidism, diabetes and rheumatoid carded by physicians as vague and affected parts. Neurological examination arthritis. Nerve entrapment can occur at unimportant, the symptoms characterised is essentially normal in most patients but the level of the tarsal tunnel adjacent to by a burning sensation, heaviness, numb- some may show a varying degree of hypo- the medial malleolus. Nerve entrapment ness, or a dull ache in the feet, can be or hyper-aesthesia.9 Knee and ankle jerks due to sciatic mononeuropathy and spinal extremely distressing to the patient. show normal to brisk reaction, but are arteriovenous malformation can also Burning is usually limited to the soles of never absent or diminished.2–4 There are cause burning feet.13,14 the feet but may ascend to involve the no signs of upper motor neuron involve- dorsum, ankles or lower legs. The arms ment such as extensor plantars or Psychosomatic causes and palms of the hands are spared. A few increased tone. Motor power is main- Burning sensations and paraesthesia are patients occasionally complain of ‘pins tained and there is no atrophy or wasting among the commonest psychosomatic and needles’ or tingling in the lower of the overlying muscles. symptoms encountered in the general extremities. Most nutritionally deficient patients population. In a study by Keshavan et al,15 Symptoms show worsening at night develop signs and symptoms of burning although many patients with burning feet with day time improvement. Patients with feet after approximately 4–5 months of had evidence of peripheral neuropathy, underlying psychiatric disorders may deficient diet. Skin manifestations of few also had psychological disorders. present with a myriad of psychosomatic vitamin deficiency such as scrotal der- signs and symptoms in association with matitis or pellagra-like rash can precede Miscellaneous causes burning feet. On examination, there is a the onset of burning sensation in the feet. Burning feet symptoms have also been paucity of objective signs. The overlying Some patients develop retrobulbar neuri- reported in various unrelated clinical con- skin and blood vessels are normal in tis as a part of vitamin deficiency ditions. Erythromelalgia, also known as most, while in some patients there may be syndrome.3 Physical examination may be erythermalgia, is an uncommon disorder accompanying erythema of the feet with entirely normal, as in familial BFS.12

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Approach to the patient Table 2. Useful diagnostic studies in BFS with burning feet As burning feet can occur in a wide spec- Suspected clinical condition Test trum of disorders, the approach to such a In all patients Complete blood count and red blood cell patient is not simple. A thorough clinical indices, routine biochemistry history and examination regarding nutri- Vitamin B deficiency or malnutrition Serum levels of B group of vitamins like tional status, vitamin deficiencies, and thiamine, riboflavin, and cyanocobalamin metabolic disorders such as diabetes and Tests for malabsorption Malabsorption syndrome (chronic hypothyroidism, and a detailed family diarrhea, postgastric surgery) Oral glucose tolerance test history are required in determining Diabetes (if signs/symptoms or risk factors further investigations. Diagnostic tests are for diabetes are present) Thyroid function tests (T3, T4, TSH) shown in Table 2. Although patients with Hypothyroidism Platelet count, bone marrow aspiration burning feet should be evaluated for a sec- Erythromelalgia (to rule out myeloproliferative diseases ondary cause, an underlying psycho- such as essential thrombocytosis or somatic illness as the cause of the symp- polycythemia vera) toms should be ruled out by psychiatric Serum and urine electrolytes assessment. Gitelman syndrome (young patients with (magnesium, sodium, potassium and fatigue, muscle weakness, cramps and chloride) Treatment fasciculations or simply asymptomatic hypokalaemia) Electrophysiological studies (nerve Treatment of BFS depends on the cause. Neuropathy, if present or strongly conduction velocities, electromyography Management can be divided into general suspected or nerve biopsy) and disease specific measures. Molecular genetic studies Familial inheritance Imaging studies such as MRI or CT General measures Mechanical cause (entrapment General treatment for all cases of BFS neuropathy) includes reassurance about the benign nature of the disorder. Wearing open and comfortable shoes, especially those with Table 3. Suggested treatment regimen for BFS with injectable arch supports, and wearing cotton socks is vitamin B preparations helpful. Soaking the feet in cold water (not ice cold) for around 15 minutes can Vitamin Dose and duration bring symptomatic temporary relief. Avoidance of feet exposure to heat Riboflavin 6–10 mg intramuscularly for 2–3 weeks should be advised. Tricyclic antidepres- Thiamine 50–100 mg intramuscularly for 2–3 weeks sants or membrane stabilising agents such Pantothenate 20–40 mg intramuscularly for 2–3 weeks as carbamazepine or gabapentin may be Nicotinic acid 100 mg intramuscularly for 2–3 weeks used for symptomatic relief. Cyanocobalamin 1000 µg 3–4 times a week for one week followed by Disease specific measures twice a week for another week As most cases of BFS occur as a conse- quence of malnutrition or vitamin deficiency, it is important to elucidate nitroglycerine therapy may alleviate pain feet, orthotics may help restore the foot’s which particular vitamin is responsible and burning.22 In erythromelalgia, treat- arch. If inflammation of the nerve is for the condition. A suggested vitamin B ment with aspirin typically produces causing the compression, nonsteroidal treatment regimen is shown in Table 3 if rapid but short lived relief of symptoms. anti-inflammatory drugs (NSAIDs) may a deficiency is detected. In patients with Elevation, cooling of limbs and systemic be prescribed. In patients where pain is diabetes, small doses of insulin in addi- analgaesia may be helpful. In mechanical not relieved by NSAIDs, local injectable tion to oral hypoglycaemic agents, cases such as tarsal tunnel syndrome, steroids may be beneficial. Surgical adequate calories and vitamin supple- conservative treatment with arch sup- decompression to relieve nerve entrap- ments are helpful. Local application of ports and wider shoes may successfully ment may be needed if conservative capsaicin ointment and percutaneous relieve discomfort. If BFS is due to flat measures fail.

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