Erythromelalgia, also known as Mitchell's isease (after Silas Weir Mitchell), red neuralgia, or erythermalgia, is a rare disorder in which blood vessels, usually in the lower extremities, are episodically blocked and inflamed. There is severe burning pain and skin redness associated with this blood vessel blockage. The attacks are periodic and are commonly triggered by heat, alcohol consumption, or exertion. Erythromelalgia can 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, hypercholesterolemia, mushroom or mercury poisoning, and some autoimmune disorders. Primary erythromelalgia is caused by mutation of the voltage-gated sodium channel α-subunit gene SCN9A.