Erythema induratum of Bazin after intravesical Bacillus Calmette-Guérin immunotherapy.

Bacillus CalmetteGuérin (BCG) is a liveattenuated strain of Mycobacterium bovis. It is recognised as an effective agent for the treatment of superficial bladder cancer and has been used in the form of a vaccine primarily against tuberculosis infections. Both applications are not devoid of complications.1 Intravesical BCG can be associated with local and systemic infectious complications which are usually selflimited, but in about 5% of patients serious side effects can occur.1 BCG vaccination on the other hand is notoriously known for its cutaneous side effects. Overall, localised abscesses, ulcers or regional suppurative lymphadenitis are the most common complications.2 Disseminated disease is much rarer and is usually associated with cellmediated immune deficiencies.2 Nonetheless, when dissemination occurs it often results in mortality.2 Here we present a unique cutaneous complication due to intravesical BCG: erythema induratum (EI) of Bazin. A 69yearold woman with bladder cancer presented to us for recurrent, disseminated, tender lesions over the trunk and extremities associated with highgrade fever. The lesions appeared 1 month after the last dose of intravesical Bacillus CalmetteGuérin (BCG). The patient was referred to us for persistent lesions and fever, not responding to levofloxacin and systemic corticosteroids. On exam, erythematoviolaceous subcutaneous nodules on the legs were appreciated (Figure 1). Similar smaller papules on the lower back, trunk, and upper extremities were noted as well. Initial blood workup was nonrevealing. A computed tomography of the chest and abdomen revealed scattered lymphadenopathy. Three sets of blood cultures, bacterial identification by 16s DNA sequencing, acidfast bacilli (AFB) smear and mycobacterial culture were nonrevealing. PPD and urine Mycobacterium tuberculosis PCR and AFB smear were negative as well. Histological examination of the nodules revealed a predominantly lobular panniculitis with mixed inflammatory cell infiltrate composed of lymphocytes, neutrophils, eosinophils, and histiocytes with focal granuloma formation (Figure 2A). Focal necrosis and vasculitic changes of small vessels were also noted (Figure 2B). Bacterial, fungal, mycobacterial cultures, AFB smear, special stains and TB PCR failed to identify any organisms. These findings were highly suggestive of EI. The patient showed significant improvement 6 months after starting prednisone and antituberculosis therapy with rifampin, isoniazid and ethambutol. Followed by a mild relapse after treatment discontinuation which eventually selfresolved. Erythema induratum is primarily regarded as a tuberculid since it occurs more frequently in populations with a high prevalence of tuberculosis, with frequent detection of mycobacterial DNA in the cutaneous lesions. Tuberculids are a cutaneous hypersensitivity towards the presence of the bacilli elsewhere in the body.3 They usually appear in patients who can mount a strong immunity against the Mycobacterium resulting in its destruction. However, there are cases of EI not linked to infections with tuberculosis; these are better labelled as nodular vasculitis.4 Clinically, EI is characterised by tender erythematous nodules and plaques, most often on the lower legs. The lesions are persistent, recurrent, can heal with scarring, and may ulcerate. The histopathological features combine a lobular or mixed panniculitis and