A rare skin disease characterized most typically by targetoid papules with concentric color variation symmetrically distributed on the extensor surfaces of the extremities, accompanied by mucosal involvement (in particular the oral mucosa) in the form of initial erythema with edema, progressing to superficial erosions with pseudomembrane formation. Grouping of lesions around the elbows and knees and edema of the nail folds may also be observed. The condition is commonly proceeded by prodromal symptoms of malaise, fever, and myalgias, and is usually self-limiting, although recurrent disease is seen in a subset of patients. [from
ORDO]