Erythema nodosum (EN) is a cutaneous reaction pattern characterised by erythematous tender nodules. Generally it is idiopathic, but it has also been associated with numerous diseases. In particular, the association of EN and tuberculosis (TBC) is well known in the literature, so all EN patients need to be evaluated for the risk of TBC: chest X-ray and tuberculin skin test should be performed. The manifestation of EN secondary to TBC infection remains a challenge for health professionals as the correct diagnosis of the primary aetiology has important therapeutic implications. The paper describes the case of a 3-year-old male presenting with EN unexpectedly diagnosed with TBC. When it comes to treatment strategy there is an ongoing discussion on whether the association TBC-EN should be treated as active or latent TBC. Experts argue that antitubercular therapy should be initiated for EN in patients with positive tuberculin skin test with or without a positively identified focus of infection.