 expanded access program (EAP). This program was available for patients with NSCLC failing platinum-based chemotherapy in the first-line metastatic setting.

![Images showing no evidence of PTB pre-treatment **(A)**, while **(B,C)** show development of PTB during administration of nivolumab. **(D)** shows a follow-up radiological investigation demonstrating cancer progression. **(A)** Initial disease progression (2 Apr 2014). **(B,C)** PTB infection during nivolumab treatment (22 Apr 2016). **(D)** Progression of disease (9 May 2016).](fonc-09-00659-g0001){#F1}

The patient experienced clinical improvement on nivolumab. However, in early 2016 she developed new symptoms of shortness of breath, cough and weight loss. A CT scan of the chest showed evidence of progressive disease, with new nodules bilaterally as well as new features of lymphangitis carcinomatosis. ([Figures 1B,C](#F1){ref-type="fig"}). The new infiltrate was evident on the two different scans. An increasing right lung infiltration was noted, which was radiologically reported as either a secondary infection or disease progression. Pneumonitis was a differential diagnosis at the time.

The patient was hospitalized as her symptoms were severe. She was treated with intravenous corticosteroids and broad-spectrum antibiotics for possible bacterial infection. The infiltrate was atypical and sputum was tested for acid-fast bacilli (AFB) to check for PTB. It is relevant to note that this patient came from a good socioeconomic area with no known exposure to TB. Her HIV status was negative. Sputum test was positive for AFB with numerous organisms observed microscopically (\>10 per field in 20 fields). The patient was referred to an infectious diseases specialist for PTB management (isoniazid, ethambutol, rifampicin and pyrazinamide). She improved clinically and was discharged on anti-TB medication and steroids tapered.

An attempt was made to restart nivolumab therapy, but the patient developed grade 2 diarrhea. After infectious causes were excluded, the diarrh