[Erythema nodosum as a reaction pattern: a broad spectrum of underlying causes]

Erythema nodosum is a skin disorder that is characterised by the presence of painful erythematous nodules and plaques, mainly located on the shins. This disorder is associated with comorbidities and can be considered as an aspecific reaction pattern to a broad range of causes. However, an idiopathic variant also exists, which occurs in 22-72% of cases. Erythema nodosum is pre-eminently a skin disease which, due to its multifactorial pathogenesis, occurs in a wider field than dermatology alone. Therefore, knowledge of this disorder is important for all practicing physicians. To illustrate this we describe three patients with erythema nodosum attributable to different causes.