Granulomatous disease can become quite extensive. Here are numerous confluent granulomas in upper lung fields in a case of active pulmonary tuberculosis. Recall that granulomatous inflammation can lead to caseous necrosis. Granulomas tend to develop and persist over months to years.

Question: What infectious disease most likely is present here?

AnswerTuberculosis is the most common cause for granulomatous lung disease. The most likely causative agent is Mycobacterium tuberculosis. A third of persons on earth have been infected, though most of these infections are subclinical.