Erythema induratum of bazin: role of polymerase chain reaction in diagnosis

A 55-year-old man presented with recurrent multiple ulcerative nodules and plaques of 1-year duration over the lower extremities. They were recalcitrant to topical (hydrocortisone cream) and systemic (pentoxyfylline, cefotiam) drugs. Skin surface examination of the affected areas showed the skin to be studded with violaceous nodules and/or plaques. A few of these had draining ulcers. The nature of the fluid was serosanguous. The lesions were located on the shins of the legs (Fig. 1). They were bilateral and asymmetrical. In addition, nontender, erythematous nodules of annular configuration were located on the right knee and elbow, and a few toes. The arterial pulsation was within normal limits. Serial hematoxylin-eosin stained sections prepared from a representative lesion were marked by the presence of palisading granulomatous dermatitis (Fig. 2). A granulomatous folluculitis in the deep dermis and a thrombotic arteriole in the subcutis were also found. Sections counter-stained for the presence of acid-fast bacilli were negative. Paraffin-embedded biopsy specimens were subjected to DNA analysis using the IS6110 gene as a polymerase chain reaction (PCR) primer, and were found to be positive. Serial chest X-rays taken at an interval of 4 months showed findings indicative of active pulmonary tuberculosis. Anti-tubercular therapy (ATT) comprising 450 mg of rifampicin, 300 mg of isoniazid, 800 mg of pyrazinamide and 1500 mg of ethambutol was administered for a period of 2 months followed by 450 mg of rifampicin and 300 mg of isoniazid for another 2 months. There was perceptible healing of the lesions, leaving atrophic and hyperpigmented scars.