A 66-year-old Caucasian male Physician Assistant was evaluated at the Infectious Disease clinic for ten-pound weight loss and worsening dry cough without fevers, night sweats or hemoptysis. He had a history of controlled type 2 diabetes mellitus, hypertension, dyslipidemia and remote history of latent tuberculosis treated in 1973 with 6 months of isoniazid. He smoked one pack of cigarettes per day during his early adulthood and quit smoking more than 40 years ago. On examination, he appeared weak and anxious with a weight 83 kg that appeared appropriate for his 185-cm height. He had a normal respiratory rate of 16 per minute, pulse of 78 per minute, and a blood pressure of 127/76 mmHg. Chest auscultation revealed good breath sounds with few left upper lobe rhonchi without crackles. The remainder of his exam was normal. Laboratory work-up revealed a white blood cell count of 5600/mm3, with 53.2% neutrophils, 29.2% lymphocytes, 11.9% monocytes, 3.8% eosinophils, hemoglobin 14.3 g/dL and platelet count 219,000/mm. The comprehensive metabolic panel was within normal limits and his HIV 1/2 antibody screen was negative.
Chest CT scan showed left upper lung lobe mass measuring 3.1 x 2.6 x 2.2 cm with smaller lower lobe lung nodules and mild left hilar adenopathy (Fig. 1). PET scan followed with findings concerning for malignancy. However, CT guided FNA biopsy was done and showed no evidence of malignant cells with negative routine, fungal and mycobacterial cultures. The patient was referred to cardiothoracic surgery and underwent thoracotomy and partial lobectomy with resection of the lung mass. Pathology exam revealed necrotizing granuloma with acid fast bacilli (Fig. 2).
Mycobacterial culture grew Mycobacterium chimaera. Confirmation and susceptibility testing were completed at the National Jewish Medical Center Mycobacteriology Laboratory in Denver, CO with molecular probes using 16S rDNA sequencing and rpoB sequencing. The isolate showed susceptibility/ intermediately susceptibility to clarithromycin, rifabutin and ethambutol with minimum inhibitory concentrations of 4 mcg/ mL, 0.5 mcg/ mL and 8mcg/mL, respectively. It showed resistance to ciprofloxacin, moxifloxacin, linezolid and amikacin with minimum inhibitory concentrations of 16 mcg/mL, 4 mcg/mL, 64 mcg/mL and 16mcg/mL, respectively.
The patient was initially treated with a 3-drug regimen including Rifabutin, Clarithromycin and Ethambutol. He had gastrointestinal intolerance to Clarithromycin, and it had to be switched to Azithromycin after 2 months. He also developed an allergic reaction to Rifabutin 6 months into therapy in the form of drug fever and eosinophilia and the drug had to be stopped. He completed the remaining 12 months of antimycobacterial therapy with Azithromycin and Ethambutol with complete resolution of his clinical and radiologic manifestations.
Initial CT scan of the chest showing left lung mass (arrow), nodules and hilar adenopathy (arrowheads).