Erythema induratum of Bazin. A clinicopathological study of 20 cases and detection of Mycobacterium tuberculosis DNA in skin lesions by polymerase chain reaction.

Erythema induratum of Bazin (EIB) is a chronic, recurring panniculitis that is found predominantly on the legs of women with tuberculin hypersensitivity. A causal relationship between EIB and Mycobacterium tuberculosis remains elusive because of the absence of demonstrable organisms in skin lesions. We reviewed the clinicopathological features of 20 patients (all women) with positive Mantoux tests (1:10,000 dilution) and characteristic skin lesions of EIB that cleared up with combined antituberculous treatment. Histological examination of skin lesions confirmed panniculitis with varying combinations of granulomatous inflammation, primary vasculitis, and necrosis. Sections from 20 formalin-fixed, paraffin-embedded skin biopsies obtained from the 20 patients were submitted for polymerase chain reaction (PCR) using oligonucleotide primers for the detection of a 123-bp DNA fragment specific for the M. tuberculosis complex. M. tuberculosis DNA was identified in five of the 20 biopsies. Meticulous care was taken to prevent contamination as a source of false-positive results. Mycobacterial DNA was absent in all negative controls and in normal skin biopsies from purified protein derivative-positive patients with and without EIB. These results provide direct evidence that mycobacterial components are present in EIB lesions and strongly suggest that M. tuberculosis is involved in the pathogenesis of EIB.