An 80-year-old Japanese female was hospitalized due to swollen cervical lymph nodes. She had no previous history of TB treatment. Her cervical Computed Tomography scan (Figure 1) findings showed multiple swollen lymph nodes, mainly in the left neck. Furthermore, laboratory studies revealed a serum C-reactive protein level of 0.26 mg/dL and lactate dehydrogenase level of 233 IU/mL (Table 1).
We present an outline of the microbiological findings in Table 2. The patient was suspected of having tumors of the lymph nodes. Three weeks after the first examination, an incision biopsy of a cervical lymph node was performed for diagnostic purposes. The histopathological findings from the biopsy tissue (Sample A) revealed necrotizing granulomas. Therefore, the patient was suspected of having an infection of acid-fast bacteria in the lymph nodes. Laboratory studies revealed a positive enzyme-linked immunospot assay for tuberculosis (ELISPOT) and were negative for immunoglobulin A antibodies against Mycobacterium avium complex-specific glycopeptidolipid core antigen (Capilia MAC) (Table 1).
Five weeks after the first examination, an incision rebiopsy of a cervical lymph node (Sample B) was performed for culture and PCR analysis of the tissue. The histopathological findings from the rebiopsy tissue (Sample B) revealed necrotizing granulomas, too. PCR analysis of a biopsy sample using the Cobas TaqMan revealed a positive result for Mycobacterium avium and a negative result for Mycobacterium tuberculosis. The patient was thus diagnosed as having Mycobacterium avium lymphadenitis. Seven weeks after the first examination, clarithromycin 800 mg, rifampicin 450 mg, and ethambutol 500 mg were started for daily administration.
Nine weeks after the first examination, a culture of acid-fast bacteria from rebiopsy tissue (Sample B) was positive in liquid culture medium. A culture of rebiopsy tissue was done at medical laboratory in Toyama Prefectural Central Hospital. PCR analysis of a cultured colony using the Cobas TaqMan revealed a negative result for Mycobacterium avium and a positive result for Mycobacterium tuberculosis. These findings suggested that the patient not had only Mycobacterium avium lymphadenitis but also tuberculous lymphadenitis, and thus isoniazid 300 mg daily was added to her regimen.
Questioning the paradoxical PCR results, we analyzed a remaining frozen specimen from sample A by PCR using the Cobas TaqMan. This analysis revealed a positive result for Mycobacterium avium and a negative result for Mycobacterium tuberculosis. All PCR analyses were carried out at the same private clinical laboratory testing facility in Japan. Next, an alternative original PCR method on a frozen specimen of sample A was conducted by the Research Institute of Tuberculosis. This PCR analysis of sample A revealed a negative result for Mycobacterium avium (negative of IS1311 and DT1) and a positive result for Mycobacterium tuberculosis (positive of IS6110). Finally, a separation of viable bacteria in cultured colonies revealed no Mycobacterium avium colonies and all Mycobacterium tuberculosis colonies by PCR using the Cobas TaqMan. Thus, it was suggested that the patient did not have Mycobacterium avium lymphadenitis but tuberculous lymphadenitis, and clarithromycin was discontinued from her regimen.
The patient continued treatment for tuberculous lymphadenitis with antitubercular drugs and experienced a reduction in cervical lymph node swelling.