Erythema gyratum repens (EGR) is a figurate erythema that is believed to be a paraneoplastic process. [1, 2, 3, 4] In addition to other features, characteristic concentric erythematous bands forming a wood-grain appearance help distinguish erythema gyratum repens from other figurate erythemas, such as erythema annulare centrifugum, erythema migrans, and erythema marginatum. 
The pathogenesis of erythema gyratum repens remains unknown. The following hypotheses have been proposed:
First, tumor antigens may form and cross-react with endogenous skin antigens.
Second, tumor products may alter endogenous skin antigens making them susceptible to autoimmune recognition.
Third, tumor antigens may form immune complexes with antibodies, which are then deposited into cutaneous tissue.
A mechanism explaining the clinically apparent migrating erythema also has been proposed. This model involves a localized ground substance phenomenon. Granulocytes release factors that stimulate proliferating fibroblasts, producing ground substance with increased viscosity. This viscous ground substance serves to impede or "wall off" the tissue spread of inflammatory mediators. In erythema gyratum repens, the advancing erythema may represent the advancement of inflammatory mediators through stroma that is unable to keep them walled off.
Erythema gyratum repens is believed to be rare. A clinical review in 1992 by Boyd cited 49 patients reported in the literature.  A current literature search yielded a handful of additional case reports.
Erythema gyratum repens reportedly occurs predominantly in white persons.
Male-to-female ratio is 2:1.
Erythema gyratum repens usually occurs in patients older than 40 years, with a mean age of 63 years, but it has been reported to occur from age 16-77 years. 
The prognosis for erythema gyratum repens depends on the underlying illness. In most patients, symptoms disappear with the resolution of underlying disease. No specific complications are associated with the skin manifestations of erythema gyratum repens, and the condition alone does not lead to death. Symptoms include intense pruritus, and morbidity and mortality may occur related to the underlying condition.