Erythema induratum of Bazin (EIB) is considered a tuberculide reaction and consists of recurrent painful nodules predominantly on the calves. Clinically it has common features with diseases like nodular vasculitis, perniosis, polyarteritis nodosa and erythema nodosum. Poncet's disease is a reactive arthritis that may accompany tuberculosis. We report a case of a young woman in which the simultaneous occurrence of erythema induratum of Bazin and Poncet's disease led to a clinical picture very similar to Löfgren's syndrome. The final diagnosis was obtained by polymerase chain reaction detection of mycobacterial DNA in a skin biopsy. A systemic therapy with tuberculostatic drugs led to the disappearance of symptoms. The presented case shows the usefulness of polymerase chain reaction diagnostics in EIB patients without other clinical signs of tuberculosis and a confusing combination of symptoms, and further confirms the presence of mycobacterial DNA in EIB lesions.