Erythema induratum with pulmonary tuberculosis: histopathologic features resembling true vasculitis

A 22-year-old South Korean woman presented with a 4-month history of severa l nodules on both legs. She looked healthy, but suffered from tenderness an d swelling of the legs. Physical examination showed multiple, nonulcerating , erythematous nodules occurring on the calves, knee joints, and thighs (fi g. 1). A biopsy specimen of the skin revealed necrotizing vasculitis of med ium-sized arteries with fibrinoid necrosis at the border between the dermis and the subcutis. Dense cellular infiltrates, including numerous neutrophi ls and lymphocytes, presented within and around the vessel walls as in poly arteritis nodosa, with some eosinophils (Fig. 2A,B). There were no other ge neralized symptoms. She was diagnosed with cutaneous polyarteritis nodosa a nd was initially treated with systemic steroids. She was given an intraveno us injection of Solu-Cortef, 60 mg/6 h for 7 days. This was replaced with o ral prednisolone for 2 weeks. The skin lesions and symptoms improved. Six months later, she complained of general weakness and recurrent skin les ions. Purified protein derivative (PPD) test gave a moderate positive react ion and chest X-ray examination showed the features of pulmonary tuberculos is: radio-opaque infiltrations in the right lower lung field. A repeated bi opsy revealed mild vasculitis with more diffuse lobular infiltrations of th e subcutaneous tissue compared with the former specimen. Polymerase chain reaction (PCR) and tissue culture for Mycobacterium tuberc ulosis were performed from a biopsy specimen. DNA was extracted from skin t issue with an Aplisystem(TM) DNA/RNA detection kit using the resin-mediated boiling method (Stargene, Seoul, South Korea). The primers were designed o n the basis of the M. tuberculosis gene IS6110 target (sense primer, 5'-CCA GAT GCA CCG TCG AAC GGC TGA T-3'; antisense primer, 5'-CGC TCG CTG AAC CGG ATC GAT GTG T-3'). The amplification was performed with uracil-N-glycosyla se (UNG), to prevent carry-over contamination, and internal control primers , to correct for false-negative reaction (Kox LF, Rhienthong D, Miranda AM, et al. A more reliable PCR for detection of Mycobacterium tuberculosis in clinical samples. J Clin Microbiol 1994; 32: 672-678; Longo MC, Berninger M S, Hartley JL, Use of uracil DNA glycosylase to control carry-over contamin ation in polymerase chain reactions. Gene 1990; 93: 125-128). According to the manufacturer's instructions, amplification was carried out for 40 cycle s with denaturation at 94 degreesC for 40 s, annealing at 70 degreesC for 1 min, and extension at 72 degreesC for 1 min in a thermal cycler (Perkin-El mer Cetus, Norwalk, CT, USA). The results of PCR and tissue culture for M, tuberculosis using the biopsy specimen were all negative (Fig.3). The patient was finally diagnosed with erythema induratum with pulmonary tu berculosis and was started on antituberculosis medication (isoniazid 400 mg , rifampicin 600 mg, ethambutol 800 mg, and pyrazinamide 1500 mg daily). Sh e showed prompt improvement after 2 weeks of medication. After 9 months of antituberculosis therapy, her skin lesions and chest X-ray had cleared. She was followed up for 4 months with no recurrence of skin and pulmonary lesi ons.