Erythromelalgia is a rare clinical syndrome that is characterized by episodic intense burning pain and marked erythema usually on the distal extremities1. It is classified as a primary or secondary condition depending on whether there are underlying diseases, such as myeloproliferative disease, autoimmune disease, and neurological disorders. We report a case of atypical clinical presentation of erythromelalgia.

A 74-year-old woman presented with a large annular erythematous to purpuric patch on her left chest that had persisted for 6 months (Fig. 1A). She reported that sensory functions on the left face, neck and chest had diminished after neurosurgery for cervical syringomyelia 30 years ago. She complained a burning and heating sensation on the lesion and flushing of the ipsilateral neck and ear, which was somewhat relieved by cooling. This was the fourth time that the patch had occurred at the same location for 10 years. The previous episodes used to occur suddenly and regress spontaneously over several weeks. She denied any preceding psychologic events or other concomitant symptoms. She said the elevation of the body temperature seemed to worsen the symptom. She has not had any other therapy like acupuncture. The patient had no other medical history except for osteoporosis and no remarkable family history. Laboratory tests, including complete blood count, blood chemistry, erythrocyte sedimentation rate, and antinuclear antibody levels were within normal limits or negative. Prothrombin time and activated partial thromboplastin time were also in normal values. Histopathological findings were nonspecific except for dilated capillaries in the dermis (Fig. 2A, B). There was no vasculitis nor erythrocyte extravasation. These findings were the same as when she had previously visited our department for the same chief complaint 6 years prior in 2009 (Fig. 1B, 2C, 2D). The human herpes virus 8 stain was negative.

Based on the clinical and histopathological findings, we diagnosed the patient with erythromelalgia on the chest. We assumed that it was secondary to syringomyelia because the skin lesion was confined to the area of neurologic abnormality. The clinical progress of the erythromelalgia waxed and waned despite treatment with low-dose oral steroids, aspirin, and gabapentin. It sustained for 3 months more and regressed spontaneously without medication.

Erythromelalgia is usually triggered by heat exposure or exercise, and it tends to be alleviated by cooling2. Although it commonly involves the feet and hands, erythromelalgia can also occur on the face or ears13. Histopathological findings are often nonspecific2. Because there is no confirmatory diagnostic test, clinical suspicion, along with a detailed history and physical examination during episodes, is required to establish a diagnosis. The differential diagnosis of this case should be early stage of Kaposi sarcoma, and painful bruising syndrome. The human herpes virus 8 stain was negative and the clinical course was not compatible with Kaposi sarcoma in that the lesion had occurred abruptly and regressed spontaneously. Painful bruising syndrome (psychogenic purpura, autoerythrocyte sensitization syndrome) shows recurrent bruise or ecchymosis with psychologic events. However, the lesion of the present case was not exactly an ecchymosis in the clinical and histopathologic findings, but rather a well-defined erythematous to purpuric patch, and had lasted several weeks to months. The recurrent episodes of the lesion had not been associated with emotional provocation.

The exact pathological mechanism of erythromelalgia remains unclear. Primary erythromelalgia is classified as a channelopathy caused by autosomal dominant mutations in SCN9A, which encodes the sodium channel alpha subunit4. Secondary erythromelalgia may accompany a number of diseases, including myeloproliferative disease with thrombocythemia, diabetes, hypertension, rheumatoid arthritis, systemic lupus erythematosus, infectious diseases, and musculoskeletal and neurological disorders1. Therefore, once a diagnosis is established, potential secondary causes must be excluded.

We have found 11 cases of erythromelalgia associated with spinal cord pathology in the literature14, and one case report of erythromelalgia presenting on the face, ear and chest in a healthy young woman of European descent5.

The natural clinical course of erythromelalgia varies. Although there are descriptions of many therapeutic regimens, such as aspirin, neuroleptics, and vasoactive agents, the optimal therapy remains unclear12. Our patient did not response to drug therapy, and her erythromelalgia regressed spontaneously.