The clinical differentiation must be made with erythema rigidum, which has a slow onset, occurs on the flexor side of the calf, is usually small in number, and the nodules may fuse with each other to form plaques, which may break down. The disease also needs to be differentiated from lipofuscinosis: lipofuscinosis is mainly located in the chest, abdomen, femur, and buttocks, appears in clusters, disappears with local atrophy and disc-shaped depressions, has fever in each episode, and has pathological changes of small vasculitis and inflammatory cell infiltration in the fatty septa. Other systemic diseases with erythema nodosum, such as Behçet’s disease, nodular disease and ulcerative colitis, have other areas of damage in addition to erythema nodosum of the skin.