[The tuberculid concept from the current viewpoint].

Abstract

The concept of tuberculid was introduced by Darier in 1896. In contrast to "true" cutaneous tuberculosis, properties of the tuberculids were explained by an hyperergic response to myobacteria or their fragments released from a different site of manifest or passed tuberculous infection. Key features include a strongly positive tuberculin skin test, evidence of concomitant manifest or past tuberculosis, and prompt response to antituberculous therapy. The inability to culture M. tuberculosis or to demonstrate it microscopically from lesional biopsies, together with reports on tuberculid-like eruptions after BCG vaccination, supports this concept. Clinical manifestations are lichen scrophulosorum, papulo-necrotic tuberculids and erythema induratum of Bazin. The existence of tuberculids has been questioned, however, because the clinical and histological appearances are not always specific. An increasing number of case reports on tuberculids, new immunological tests and molecular biology-based techniques for the detection of mycobacteria have shed new light on the tuberculid concept.