Erythema induratum of Bazin—A subcutaneous granulomatous vasculitis that caused difficulty in walking

A 63-year-old diabetic man presented with progressive red nodules on the anterior-lateral side of both legs (Figure 1) with worsening pain. C-reactive protein was elevated (3.81 mg/dL). D-dimer and venous ultrasonography were normal. The interferon-gamma release assay (IGRA) and tuberculin test were both positive without chest radiologic abnormalities. Histopathology of the nodules showed lobular inflammation with subcutaneous vasculitis (Figure 2A), and histiocyte and neutrophil infiltration with vascular destruction (Figure 2B–D). There were no caseating granulomas nor acid-fast bacilli, and Mycobacterium tuberculosis PCR was negative. The patient was diagnosed with erythema induratum of Bazin (EIB) and he underwent antituberculous therapy with a four-drug regimen for seven months without steroid use. He began to walk three weeks after treatment initiation and his erythema induratum resolved within two months. EIB is a rare subcutaneous granulomatous disease caused by an autoimmune reaction to M. tuberculosis (Mascaro and Baselga, 2008Mascaro Jr, J.M. Baselga E. Erythema induratum of bazin.Dermatol Clin. 2008; 26: 439-445Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar). It frequently occurs in the lower extremities and accompanies diabetes (Kara Polat et al., 2020Kara Polat A. Gore Karaali M. Esra Koku Aksu A. Asli Turgut Erdemir V. Leblebici C. Salih Gurel M. A rare cutaneous tuberculosis form, erythema induratum of Bazin: 6 years’ experience.Acta Dermatovenerol Alp Pannonica Adriat. 2020; 29: 123-128PubMed Google Scholar). Its histology is characterized by lobular panniculitis with vasculitis (Segura et al., 2008Segura S. Pujol R.M. Trindade F. Requena L. Vasculitis in erythema induratum of Bazin: a histopathologic study of 101 biopsy specimens from 86 patients.J Am Acad Dermatol. 2008; 59: 839-851Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar). The majority of cases of EIB respond to antituberculous treatment (Magalhaes et al., 2018Magalhaes T.S. Dammert V.G. Samorano L.P. Litvoc M.N. Nico M.M.S. Erythema induratum of Bazin: Epidemiological, clinical and laboratorial profile of 54 patients.J Dermatol. 2018; 45: 628-629Crossref PubMed Scopus (6) Google Scholar), therefore IGRA and skin biopsy should be performed to avoid diagnostic delay. The patient consented to image publication and provided written consent. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.