Authors’ reply

We, as rheumatologists, greatly appreciate the insights regarding our article published in Polish Archives of Internal Medicine¹ by Skowroński² from the Tuberculosis Department of Wielkopolska Center of Pulmonology and Thoracic Surgery.

We are aware that the QuantiFERON‑TB test (QTF; QIAGEN, Venlo, the Netherlands) is not a test confirming tuberculosis (TB) but rather a screening tool used to detect patients at a risk of TB. The conversion of QTF from negative (obtained prior to the introduction of antitumor necrosis factor α agent as a part of routine screening) to positive at the time of the patient’s hospitalization was a clue, not a confirmation of TB diagnosis.

As mentioned in our article, typically “TB diagnostic workup includes sputum examination, autofluorescence bronchoscopy, culture, and a PCR test,” while in our case “the patient did not cough up sputum which could be collected for examination” and “quick blood and urine polymerase chain reaction (PCR) tests for Mycobacterium tuberculosis (…) were negative.”¹

We agree that the diagnostic process performed at our Department of Rheumatology and Internal Medicine did not provide microbiological results that would allow for a sharp distinction between TB and nontuberculous mycobacteria (NTM) pulmonary disease—hence the thought‑provoking title and the use of a broad term “mycobacteriosis” throughout the article.

Microbiology is an essential part of the TB diagnostic process and we concur that this case warranted bronchoscopy, a key test to obtain both cultures for TB/NTM, and biopsy due to a suspicion of cancer. However, bronchoscopy was not possible to perform at the time. As explained in our article, the patient was judged unsuitable for bronchoscopy by a consulting pulmonologist who based her decision on the radiologic (in hindsight, incorrect) diagnosis of disseminated lung malignancy and the patient’s poor general condition. We should add that the radiologist was given an opportunity to re‑evaluate computed tomography images specifically in the context of suspected TB, after obtaining a positive QFT result, but reconfirmed the initial diagnosis of metastatic cancer. The antimycobacterial therapy was introduced despite the radiologist’s and pulmonologist’s opinions, somewhat as a last resort in a rapidly deteriorating patient, in the absence of sufficient evidence for or against either TB or cancer.

The diagnosis of a mycobacterial infection was inferred due to the patient’s recovery on antimycobacterial treatment. The therapy was applied for 6 months with follow‑ups at an outpatient pulmonology clinic, and no side effects were observed. Levofloxacin, which is not the first‑line anti‑TB drug, was continued in this specific scenario due to the patient’s partial improvement after introducing it earlier for presumed pneumonia.

We believe that this case report, aside from showcasing mycobacteriosis as a great mimicker, highlights the importance of a multidisciplinary approach to an immunocompromised patient, and of thinking outside the box in time‑sensitive clinical scenarios with limited diagnostic resources.