Erythromelalgia



Nomenclature

Erythros - red; melon - extremities; algos - pain = erythromelalgia.
Erythros - red; therme - heat; algos - pain = erythermalgia.

Best term would be erythermelalgia?

Presentation

Severe pain, heat and flushing of the legs, usually episodic in nature.

  • Episodes may be triggered by warming or dependency, and relieved by cooling (virtually pathognomic)
  • Episodes often begin with an itchy sensation before the flushing
  • Legs are almost always affected, feet worst and rarely above the knee
  • Arms and/or face also affected in about half
  • Usually bilateral symptoms.

Pain can begin months before flushing, leading to misdiagnosis as neuropathic pain.

Epidemiology

  • Can occur at any age, but commonest in middle age
  • Female: male about 3:1;
  • prevalence around 1:100,000.

Causes

Most are idiopathic, especially if early onset.

Erythromelalgia may be secondary to myeloproliferative disease or connective tissue disorders.

  • Erythromelalgia often precedes diagnosis of myeloproliferative disease by months; relief with aspirin may be a clue to incipient MPD.

Familial erythromelalgia (<5%) is due to a Na-channel mutation.

Raynaud's phenomenon may co-exist - ?general problem with vasoconstriction (predominant in RP) and hyperaemia (responsible for painful flushing in RP and EM).

Complications

  • Digital necrosis or ulceration can lead to amputation.
  • Constant immersion in cold water can lead to maceration and infection.
  • Rarely, hypothermia due to constant immersion.

Investigations

Erythromelalgia is a clinical diagnosis.

  • Careful history and examination for connective tissue disorders
  • FBC - ?elevated Hb, WBC, plt
  • Thermography may reveal elevated temperature in affected areas, but not required for diagnosis

Treatments

Various treatments have been reported to help - none has any decent evident base. The Erythromelalgia Association survey suggested that gabapentin had the highest rates of benefit.

  • aspirin 500mg (response may suggest myeloproliferative disorder)
  • gabapentin/pregabalin/amitriptyline/imipramine/fluoxetine/fluvoxamine
  • diltiazem/nifedipine
  • capsaicin
  • propranol
  • misoprostol
  • lidocaine
  • mexiletine, particularly for the familial form

In severe cases, the following have been described in single case reports:

  • IV nitroprusside in children
  • IV lidocaine in one adult, then maintained with mexiletine
  • sympathectomy reports variable - worth considering if improvement with sympathetic block trial?

See The Erythomelalgia Association.