Skin swelling and red rash or blisters usually in the lower
legs or arms.
also known as Mitchell's disease (after Silas Weir Mitchell),
acromelalgia, red neuralgia, or erythermalgia, is a rare
neurovascular peripheral pain disorder in which blood vessels,
usually in the lower extremities (or hands), are episodically
blocked (frequently on and off daily), then become hyperemic
and inflamed. There is severe burning pain (in the small
fiber sensory nerves) and skin redness. The attacks are
periodic and are commonly triggered by heat, pressure, mild
activity, exertion, insomnia or stress. Erythromelalgia
may occur either as a primary or secondary disorder (i.e.
a disorder in and of itself or a symptom of another condition).
Secondary erythromelalgia can result from small fiber peripheral
neuropathy of any cause, essential thrombocytosis, hypercholesterolemia,
mushroom or mercury poisoning, and some autoimmune disorders.
Primary erythromelalgia is caused by mutation of the voltage-gated
sodium channel a-subunit gene SCN9A.
In 2004 Erythromelalgia became the first human disorder
in which it has been possible to associate an ion channel
mutation with chronic neuropathic pain; this became possible
when a Yale neurologist spotted a Beijing geneticists team
paper in the Journal of Medical Genetics titled "Mutations
in SCN9A, Encoding a Sodium Channel Alpha Subunit, in Patients
With Primary Erythromelalgia"; a connection was made
that this sodium channel mutation was expressed primarily
in peripheral pain sensing neurons. Conversely, in December
2006 a University of Cambridge team reported an SCN9A mutation
that created a complete "lack of" pain sensation
in the family of a Pakistan street performer. He felt no
pain, walked on hot coals and stabbed himself to entertain
assess the frequency and type of vascular changes and neurologic
abnormalities in patients with erythromelalgia... CONCLUSION:This
prospective study extends and confirms our previous observation
that, in addition to other forms of neuropathy, most patients
with erythromelalgia have small-fiber neuropathy (small
nerves in the skin)." http://www.ncbi.nlm.nih.gov/pubmed/14568838
This study states the cause of Erythromelalgia
is that the nerves become small and do not work properly.