Erythema nodosum (EN) is the most frequent clinicopathologic variant of panniculitis with painful red or violaceous nodules on the anterior surfaces of the legs. The condition is a cutaneous reaction that might be associated with a wide variety of disorders or might be caused by medications that produce painful nodules on the shins, and less commonly on the thighs and forearms. In this paper, we describe, for the first time in the world, erythema nodosum as the simultaneous presenting complaint of monozygotic twin sisters after streptococcal pharyngitis. This paper might support the effect of heredity in the occurrence of erythema nodosum.