A case of pulmonary tuberculosis with false negative QuantiFERON TB-2G Test

A 57-year-old man was admitted to our hospital with a high fever and productive cough. He had a previous history of total gastrectomy and splenectomy at the age of 45 years due to gastric cancer. He also showed severe macrocytic anemia with low vitamin B12, and an infiltrative shadow was found in the right lung on an X-ray. Sputum examination on admission revealed no significant pathogenic bacteria, and an acid-fast stain and a M. tuberculosis PCR test were negative. QuantiFERON TB-2G Test (QFT) was negative on admission. Because pneumococcal antigen in the urine was positive, we initially diagnosed pneumococcal pneumonia and treatment with antibiotics was started. However, symptoms were not resolved with several antibiotics, finally, a thoracoscopic lung biopsy under general anesthesia was performed for a definitive diagnosis. The biopsy showed epithelioid cell granuloma in the alveolar spaces, and the 8 weeks culture of sputum taken on admission revealed M. tuberculosis. Finally, a pulmonary tuberculosis was diagnosed and treatment with four drugs of HERZ was begun. We have encountered a case of pulmonary tuberculosis combined with a lobar pneumococcal pneumonia, and negative for QFT. In general, splenectomy is known as a risk factor of pneumococcal infection. And vitamin B12 deficiency due to gastrectomy is one of the risk factors for cellular immunity impairment and was possibly to the false negative QFT and development of TB.