A 65-year-old immunocompetent man presented to our hospital with an 11-year history of a huge erythematous erosive plaque on his neck. The lesions developed from a pigeon's egg-sized nodule 11 years ago. Physical examination showed a reddish nodular plaque with superficial erosions, tough textures, well-defined borders on his neck in a size of 18 x 10 cm and verrucous proliferating nodules behind his left ear with no abnormalities on neurological examination (Figure 1). Apple jelly nodules were seen on diascopy. He was previously healthy and had no fever, dry cough, fatigue, or other complaints. He denied any history of contact with tuberculosis patients. Initially, sarcoidosis was diagnosed based on biopsies of skin lesions or lymph nodes and he was treated with prednisone acetate and azathioprine over 10 years. However, the skin lesions are still gradually expanding.
Laboratory examinations including syphilis, human immunodeficiency virus tests, peripheral blood lymphocytes count, microscopic examination of Mycobacterium leprae, IgM and IgG levels against NDO-LID as well as MMP-II for leprosy, acid-fast staining of sputum smear and anti- Mycobacterium tuberculosis antibodies showed negative results. The measurement of enzyme-linked immunospot assay for tuberculosis (T-SPOT.TB) and leprosy were also negative. A computed tomographic (CT) scan revealed multiple enlarged lymph nodes in bilateral neck, submandibular and mediastinum. Histopathological examination of the lesion on the neck showed necrosis and epithelioid-cell granuloma (Figure 2A) in the dermis, which infiltrates lymphocytes, epithelioid cells and Langhans giant cells (Figure 2B) and negative findings of periodic acid-Schiff, silver and Ziehl-Neelsen stains. Single polymerase chain reaction (PCR) tests for rpoB and hsp65 genes of the skin lesions did not identify Mycobacterium tuberculosis until nested PCR for the same genes were performed. Tissue cultures from the lesions grew caseous yellow colonies at 37 C in Lowenstein-Jensen medium after 40 days. The isolate's 16S ribosomal RNA and hsp65 gene sequence were 100% homologous to Mycobacterium tuberculosis strain FDAARGOS_756.
The patient was eventually diagnosed with lupus vulgaris. Resistance testing showed that the pathogen was sensitive to isoniazid, rifampicin, ethambutol, streptomycin and pyrazinamide.
The patient received the antituberculosis regimen including rifampin, isoniazid, ethambutol, pyrazinamide for two months followed by isoniazid and rifampicin for 4 months (2HRZE/4HR). After six months of follow-up, the lesions were almost completely cleared, leaving residual scar and hyperpigmentation (Figure 3) and the enlarged lymph nodes were smaller than before on CT scan with no adverse effects during treatment.